485BPOS

Registration No. 33-08054

File No. 811-4803

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC  20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933	x
Pre-Effective Amendment No.	o
Post-Effective Amendment No. 41	x
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940	x
Amendment No. 42	x

OPPENHEIMER MUNICIPAL FUND

(Exact Name of Registrant as Specified in Charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of Principal Executive Offices)                 (Zip Code)

(303) 768-3200

(Registrant’s Telephone Number, including Area Code)

Arthur S. Gabinet, Esq.

OFI Global Asset Management, Inc.

Two World Financial Center, 225 Liberty Street 11^th Floor, New York, New York 10281-1008

(Name and Address of Agent for Service)

It is proposed that this filing will become effective (check appropriate box):

x Immediately upon filing pursuant to paragraph (b)

o On ____________, pursuant to paragraph (b)

o 60 days after filing, pursuant to paragraph (a)(1)

o On _____________, pursuant to paragraph (a)(1)

o 75 days after filing, pursuant to paragraph (a)(2)

o On ______________, pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

o This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of New York and State of New York on the 11^th day of February, 2013.

OPPENHEIMER MUNICIPAL FUND
By:	William F. Glavin, Jr.*
	William F. Glavin, Jr.*, President, Principal Executive Officer & Trustee

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities on the dates indicated:

Signatures	Title	Date
Brian F. Wruble*	Chairman of the	February 11, 2013
Brian F. Wruble	Board of Trustees
William F. Glavin, Jr.*	President, Principal	February 11, 2013
William F. Glavin, Jr.	Executive Officer and Trustee
Brian W. Wixted*	Treasurer, Principal	February 11, 2013
Brian W. Wixted	Financial & Accounting Officer
David K. Downes*	Trustee	February 11, 2013
David K. Downes
Matthew P. Fink*	Trustee	February 11, 2013
Matthew P. Fink
Phillip A. Griffiths*	Trustee	February 11, 2013
Phillip A. Griffiths
Mary F. Miller*	Trustee	February 11, 2013
Mary F. Miller
Joel W. Motley*	Trustee	February 11, 2013
Joel W. Motley
Joanne Pace*	Trustee	February 11, 2013
Joanne Pace
Mary Ann Tynan *	Trustee	February 11, 2013
Mary Ann Tynan
Joseph M. Wikler*	Trustee	February 11, 2013
Joseph M. Wikler
Peter I. Wold*	Trustee	February 11, 2013
Peter I. Wold

*By:	/s/ Mitchell J. Lindauer
	Mitchell J. Lindauer, Attorney-in-Fact

EXHIBIT INDEX

Exhibit No.	Description
Ex-101.INS	XBRL Instance Document
Ex-101.SCH	XBRL Taxonomy Extension Schema Document
Ex-101.CAL	XBRL Taxonomy Extension Calculation Linkbase Document
Ex-101.DEF	XBRL Taxonomy Extension Definition Linkbase
Ex-101.LAB	XBRL Taxonomy Extension Labels Linkbase
Ex-101.PRE	XBRL Taxonomy Extension Presentation Linkbase Document

XML

Expense Example, No Redemption (dei_DocumentInformationDocumentAxis, (Oppenheimer Rochester® Limited Term Municipal Fund), USD $)	0 Months Ended
	Jan. 28, 2013
Class A
Expense Example, No Redemption:
Expense Example, No Redemption, 1 Year	$ 303
Expense Example, No Redemption, 3 Years	469
Expense Example, No Redemption, 5 Years	650
Expense Example, No Redemption, 10 Years	1,173
Class B
Expense Example, No Redemption:
Expense Example, No Redemption, 1 Year	165
Expense Example, No Redemption, 3 Years	512
Expense Example, No Redemption, 5 Years	883
Expense Example, No Redemption, 10 Years	1,494
Class C
Expense Example, No Redemption:
Expense Example, No Redemption, 1 Year	159
Expense Example, No Redemption, 3 Years	493
Expense Example, No Redemption, 5 Years	851
Expense Example, No Redemption, 10 Years	1,860
Class Y
Expense Example, No Redemption:
Expense Example, No Redemption, 1 Year	53
Expense Example, No Redemption, 3 Years	167
Expense Example, No Redemption, 5 Years	291
Expense Example, No Redemption, 10 Years	$ 654

XML

(Oppenheimer Rochester® Limited Term Municipal Fund)

Investment Objective. The Fund seeks a high level of current income exempt from federal income tax.

Fees and Expenses of the Fund. This table describes the fees and expenses that you may pay if you buy and hold or redeem shares of the Fund. You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $100,000 in certain funds in the Oppenheimer family of funds. More information about these and other discounts is available from your financial professional and in the section "About Your Account" beginning on page 15 of the prospectus and in the sections "How to Buy Shares" beginning on page 59 and "Appendix A" in the Fund's Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Oppenheimer Rochester® Limited Term Municipal Fund)	Class A	Class B	Class C	Class Y
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	2.25%	none	none	none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	none	4.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Oppenheimer Rochester® Limited Term Municipal Fund)	Class A	Class B	Class C	Class Y
Management Fees	0.41%	0.41%	0.41%	0.41%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none
Total Other Expenses	0.12%	0.20%	0.14%	0.11%
Interest and Related Expenses from Inverse Floaters	0.02%	0.02%	0.02%	0.02%
Interest and Fees from Borrowing	0.04%	0.04%	0.04%	0.04%
Other Expenses	0.06%	0.14%	0.08%	0.05%
Total Annual Fund Operating Expenses	0.78%	1.61%	1.55%	0.52%

Example. The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in a class of shares of the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your expenses would be as follows:

If shares are redeemed

Expense Example (Oppenheimer Rochester® Limited Term Municipal Fund) (USD $)	1 Year	3 Years	5 Years	10 Years
Class A	303	469	650	1,173
Class B	565	712	983	1,494
Class C	259	493	851	1,860
Class Y	53	167	291	654

If shares are not redeemed

Expense Example, No Redemption (Oppenheimer Rochester® Limited Term Municipal Fund) (USD $)	1 Year	3 Years	5 Years	10 Years
Class A	303	469	650	1,173
Class B	165	512	883	1,494
Class C	159	493	851	1,860
Class Y	53	167	291	654

Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 19% of the average value of its portfolio.

Principal Investment Strategies. Under normal circumstances and as a fundamental policy, the Fund invests at least 80% of its net assets (plus borrowings for investment purposes) in investment-grade municipal securities that are exempt from federal income tax (including securities subject to alternative minimum tax). Under normal market conditions and as a non-fundamental policy, the Fund will not invest more than 5% of its total assets in securities rated below-investment-grade at the time of acquisition.

Investment-grade securities are rated in one of the four highest rating categories of a nationally recognized statistical rating organization, such as Standard & Poor's (or in the case of unrated securities, determined by the Fund's investment sub-adviser to be comparable to securities rated investment-grade). The Fund also invests in unrated securities, in which case the Fund's investment sub-adviser, OppenheimerFunds, Inc., internally assigns ratings to those securities, after assessing their credit quality and other factors, in investment-grade or below-investment-grade categories similar to those of nationally recognized statistical rating organizations. There can be no assurance, nor is it intended, that the sub-adviser's credit analysis process is consistent or comparable with the credit analysis process used by a nationally recognized statistical ratings organization.

The Fund invests in municipal securities issued by the governments of states, their political subdivisions (such as cities, towns and counties), the District of Columbia, U.S. territories, commonwealths and possessions or by their agencies, instrumentalities and authorities, if the interest paid on the security is not subject to federal personal income tax (in the opinion of bond counsel to the issuer at the time the security is issued). These securities primarily include municipal bonds, municipal notes and interests in municipal leases.

The Fund seeks to maintain a dollar-weighted effective portfolio maturity of five years or less, however, it can buy securities that have short, intermediate or long maturities. Because of events affecting the bond markets and interest rate changes, the maturity of the portfolio might not meet the target at all times.

The Fund can invest substantial amounts of its assets in private activity municipal securities that pay interest that is tax-exempt but which may be a "tax-preference item" for investors subject to alternative minimum taxation. The Fund also borrows for leverage and invests in inverse floaters, a variable rate obligation and form of derivative, to seek increased income and return. The Fund can expose up to 20% of its total assets to the effects of leverage from its investments in inverse floaters. The Fund can also borrow money to purchase additional securities, another form of "leverage". Although the amount of borrowing will vary from time to time, the amount of leveraging from borrowings will not exceed one-third of the Fund's total assets.

In selecting investments for the Fund, the portfolio managers generally look for a wide range of issuers and securities nationwide that provide high current income, including unrated bonds and securities of smaller issuers that might be overlooked by other investors and funds that offer high current income. The portfolio managers also focus on securities with coupon interest or accretion rates, current market interest rates, callability and call prices that might change the effective maturity of particular securities and the overall portfolio and securities with various maturities in an effort to reduce share price volatility.

The portfolio managers may consider selling a security if any of these factors no longer applies to a security purchased for the Fund, but are not required to do so.

Principal Risks. The price of the Fund's shares can go up and down substantially. The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth more or less than what you paid for them. These risks mean that you can lose money by investing in the Fund.

Main Risks of Investing in Municipal Securities. Municipal securities may be subject to interest rate risk, credit risk, credit spread risk, extension risk, reinvestment risk and prepayment risk. Interest rate risk is the risk that when prevailing interest rates fall, the values of already-issued debt securities generally rise; and when prevailing interest rates rise, the values of already-issued debt securities generally fall, and they may be worth less than the amount the Fund paid for them. When interest rates change, the values of longer-term debt securities usually change more than the values of shorter-term debt securities. Credit risk is the risk that the issuer of a security might not make interest and principal payments on the security as they become due. If an issuer fails to pay interest or repay principal, the Fund's income or share value might be reduced. Adverse news about an issuer or a downgrade in an issuer's credit rating, for any reason, can also reduce the market value of the issuer's securities. "Credit spread" is the difference in yield between securities that is due to differences in their credit quality. There is a risk that credit spreads may increase when the market expects lower-grade bonds to default more frequently. Widening credit spreads may quickly reduce the market values of the Fund's lower-rated and unrated securities. Extension risk is the risk that an increase in interest rates could cause principal payments on a debt security to be repaid at a slower rate than expected. Extension risk is particularly prevalent for a callable security where an increase in interest rates could result in the issuer of that security choosing not to redeem the security as anticipated on the security's call date. Such a decision by the issuer could have the effect of lengthening the debt security's expected maturity, making it more vulnerable to interest rate risk and reducing its market value. Reinvestment risk is the risk that when interest rates fall the Fund may be required to reinvest the proceeds from a security's sale or redemption at a lower interest rate. Callable bonds are generally subject to greater reinvestment risk than non-callable bonds. Prepayment risk is the risk that the issuer may redeem the security prior to the expected maturity or that borrowers may repay the loans that underlie these securities more quickly than expected, thereby causing the issuer of the security to repay the principal prior to the expected maturity. The Fund may need to reinvest the proceeds at a lower interest rate, reducing its income.

Main Risks of Shorter-Term Securities. Normally, when interest rates change, the values of shorter-term debt securities change less than the values of securities with longer maturities. The Fund tries to reduce the volatility of its share prices by seeking to maintain a shorter average effective portfolio maturity. However, shorter-term securities may have lower yields than longer-term securities. Shorter-term securities are also subject to extension and reinvestment risk. The Fund is subject to extension risk when principal payments on a debt security occur at a slower rate than expected, potentially extending the average life of the security. For securities with a call date in the near future, there is the risk that an increase in interest rates could result in the issuer of that security choosing not to redeem the security as anticipated on the security's call date. Such a decision by the issuer may effectively change a short- or intermediate-term security into a longer term security, which could have the effect of locking in a below-market interest rate on the security, increasing the security's duration, making the security more vulnerable to interest rate risk, reducing the security's market value and increasing the Fund's average effective portfolio maturity. Under such circumstances, because the values of longer term securities generally fluctuate more widely in response to interest rate changes than shorter term securities, the Fund's volatility could increase. Reinvestment risk is the risk that if interest rates fall the Fund may need to invest the proceeds of redeemed securities in securities with lower interest rates.

Taxability Risk. The Fund's investments in municipal securities rely on the opinion of the issuer's bond counsel that the interest paid on those securities will not be subject to federal income tax. Tax opinions are generally provided at the time the municipal security is initially issued. However, after the Fund buys a security, the Internal Revenue Service may determine that a bond issued as tax-exempt should in fact be taxable and the Fund's dividends with respect to that bond might be subject to federal income tax.

Municipal Market Volatility and Illiquidity. The municipal bond market can be susceptible to unusual volatility, particularly for lower-rated and unrated securities. Liquidity can be reduced unpredictably in response to overall economic conditions or credit tightening. During times of reduced market liquidity, the Fund may not be able to readily sell bonds at the prices at which they are carried on the Fund's books. If the Fund needed to sell large blocks of bonds to meet shareholder redemption requests or to raise cash, those sales could further reduce the bonds' prices.

Municipal Sector Concentration. While the Fund does not invest more than 25% of its total assets in a single industry, certain types of municipal securities (such as general obligation, government appropriation, municipal leases, special assessment and special tax bonds) are not considered a part of any "industry" for purposes of this policy. Therefore, the Fund may invest more than 25% of its total assets in these types of municipal securities. These types of municipal securities may finance, or pay interest from the revenues of, projects that tend to be impacted in the same way by economic, business or political developments which would increase credit risk. For example, legislation on the financing of a project or a declining economic need for the project would likely affect all similar projects.

Special Risks of Investing in U.S. Territories, Commonwealths and Possessions. The Fund also invests in obligations of the governments of the U.S. territories, commonwealths and possessions such as the Puerto Rico, the Virgin Islands, Guam or the Northern Mariana Islands to the extent such obligations are exempt from state and/or federal income taxes, pursuant to the Fund's principal investment strategies. As applicable, these investments also are considered to be "state municipal securities" for purposes of this prospectus. Accordingly, the Fund may be adversely affected by local political and economic conditions and developments within these U.S. territories, commonwealths and possessions affecting the issuers of such obligations.

Certain of the municipalities in which the Fund invests currently experience significant financial difficulties. A credit rating downgrade relating to, default by, or insolvency or bankruptcy of, one or several municipal security issuers of a state, territory, commonwealth or possession in which the Fund invests could affect the market values and marketability of many or all municipal obligations of such state, territory, commonwealth or possession.

Risks of Land-Secured or "Dirt" Bonds. These special assessment or special tax bonds are issued to promote residential, commercial or industrial growth and redevelopment. They are exposed to real estate development-related risks. The bonds could default if the developments failed to progress as anticipated or if taxpayers failed to pay the assessments, fees and taxes specified in the financing plans for a project.

Risks of Tobacco Related Bonds. In 1998, the largest U.S. tobacco manufacturers reached an out of court agreement, known as the Master Settlement Agreement (the "MSA"), to settle claims against them by 46 states and six other U.S. jurisdictions. The tobacco manufacturers agreed to make annual payments to the government entities in exchange for the release of all litigation claims. A number of the states have sold bonds that are backed by those future payments. The Fund may invest in two types of those bonds: (i) bonds that make payments only from a state's interest in the MSA and (ii) bonds that make payments from both the MSA revenue and from an "appropriation pledge" by the state. An "appropriation pledge" requires the state to pass a specific periodic appropriation to make the payments and is generally not an unconditional guarantee of payment by a state.

The settlement payments are based on factors, including, but not limited to, annual domestic cigarette shipments, cigarette consumption, inflation and the financial capability of participating tobacco companies. Payments could be reduced if consumption decreases, if market share is lost to non-MSA manufacturers, or if there is a negative outcome in litigation regarding the MSA, including challenges by participating tobacco manufacturers regarding the amount of annual payments owed under the MSA.

The Fund can invest up to 25% of its total assets in tobacco-related bonds without an appropriation pledge that make payments only from a state's interest in the MSA.

Main Risks of Borrowing and Leverage. The Fund can borrow up to one-third of the value of its total assets (including the amount borrowed) from banks, as permitted by the Investment Company Act of 1940. It can use those borrowings for a number of purposes, including for purchasing securities, which can create "leverage." In that case, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not borrow. Borrowing results in interest payments to the lenders and related expenses. Borrowing for investment purposes might reduce the Fund's return if the yield on the securities purchased is less than those borrowing costs. The Fund may also borrow to meet redemption obligations, for temporary and emergency purposes, or to unwind or contribute to trusts in connection with the Fund's investment in inverse floaters (instruments also involving the use of leverage, as discussed below). The Fund currently participates in a line of credit with other Oppenheimer funds for its borrowing.

The Fund can participate in a committed reverse repurchase agreement program. Reverse repurchase agreements that the Fund may engage in also create leverage. A reverse repurchase agreement is the sale by the Fund of a debt obligation to a party for a specified price, with the simultaneous agreement by the Fund to repurchase that debt obligation from that party on a future date at a higher price. Similar to a borrowing, reverse repurchase agreements provide the Fund with cash for investment and operational purposes. When the Fund engages in reverse repurchase agreements, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not engage in these transactions due to the effect of leverage. Reverse repurchase agreements create fund expenses and require that the Fund have sufficient cash available to repurchase the debt obligation when required. Reverse repurchase agreements also involve the risk that the market value of the debt obligation that is the subject of the reverse repurchase agreement could decline significantly below the price at which the Fund is obligated to repurchase the security.

Risks of Derivatives. A "derivative" is an investment whose value depends on (or is derived from) the value of an underlying security, asset, interest rate, index or currency. Derivatives may be volatile and involve significant risks. Derivative transactions may require the payment of premiums and can increase portfolio turnover. Certain derivative investments may be illiquid. The underlying security or other reference on which a derivative is based, or the derivative itself, may not perform the way the Fund expects it to. The Fund could realize little or no income or lose principal from a derivative investment or a hedge might be unsuccessful. The Fund may also lose money if the issuer of a derivative fails to pay the amount due.

Inverse Floaters. The Fund invests in inverse floating rate securities ("inverse floaters") because, under ordinary circumstances, they offer higher yields and thus provide higher income than fixed-rate municipal bonds of comparable maturity and credit quality. Because inverse floaters are leveraged instruments, the value of an inverse floater will change more significantly in response to changes in interest rates and other market fluctuations than the market value of a conventional fixed-rate municipal security of comparable maturity and credit quality, including the municipal bond underlying an inverse floater.

An inverse floater is created when a fixed-rate municipal bond is contributed to a trust. The trust issues two separate classes of securities: short-term floating rate securities with a fixed principal amount that represent a senior interest in the underlying municipal bond, and the inverse floater that represents a residual, subordinate interest in the underlying municipal bond. The trust issues and sells the short-term floating rate securities to third parties and the inverse floater to the Fund. The short-term floating rate securities generally bear short-term rates of interest. When interest is paid on the underlying municipal bond to the trust, such proceeds are first used to pay interest owing to holders of the short-term floating rate securities, with any remaining amounts being paid to the Fund, as the holder of the inverse floater. Accordingly, the amount of such interest paid to the Fund is inversely related to the rate of interest on the short-term floating rate securities. Inverse floaters produce less income when short-term interest rates rise (and, in extreme cases, may pay no income) and more income when short-term interest rates fall. Thus, if short-term interest rates rise after the issuance of the inverse floater, any yield advantage to the Fund is reduced and may be eliminated. Additionally, because the principal amount of the short-term floating rate security is fixed and is not adjusted in response to changes in the market value of the underlying municipal bond, any change in the market value of the underlying municipal bond is reflected entirely in a change to the value of the inverse floater. Upon the occurrence of certain adverse events, a trust may be collapsed and the underlying municipal bond liquidated, and the Fund could lose the entire amount of its investment in the inverse floater and may, in some cases, be contractually required to pay the negative difference, if any, between the liquidation value of the underlying municipal bond and the principal amount of the short-term floating rate securities.

The Fund may invest in inverse floaters with any degree of leverage (measured by comparing the outstanding principal amount of related short-term floating rate securities to the par value of the underlying municipal bond). However, the Fund may only expose up to 20% of its total assets to the effects of leverage from its investments in inverse floaters. This limitation is measured by comparing the aggregate principal amount of the short-term floating rate securities that are related to the inverse floaters held by the Fund to the total assets of the Fund. Nevertheless, the value of, and income earned on, an inverse floater that has a higher degree of leverage (represented by a larger outstanding principal amount of related short-term floating rate securities) will fluctuate more significantly in response to changes in interest rates and to changes in the market value of the related underlying municipal bond, and are more likely to be eliminated entirely under adverse market conditions.

Who Is the Fund Designed For? The Fund is designed for investors seeking a high level of current income exempt from federal income tax. Due to the Fund's emphasis on investment-grade securities and an intermediate effective average maturity intended to reduce overall portfolio volatility, the Fund's yield may be lower than longer-term municipal bond funds or municipal bond funds that can invest more of their assets in lower-grade investments. Because it invests in tax-exempt securities, the Fund is not appropriate for a retirement plan or other tax-exempt or tax-deferred account. The Fund is not a complete investment program. You should carefully consider your own investment goals and risk tolerance before investing in the Fund.

An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

The Fund's Past Performance. The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance (for Class A shares) from year to year and by showing how the Fund's average annual returns for 1, 5 and 10 years compare with those of a broad measure of market performance. The Fund's past investment performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. More recent performance information is available by calling the toll-free number on the back of this prospectus and on the Fund's website: https://www.oppenheimerfunds.com/fund/LimitedTermMunicipalFund

Sales charges and taxes are not included and the returns would be lower if they were. During the period shown, the highest return for a calendar quarter was 7.00% (3rd Qtr 09) and the lowest return was -10.29% (4th Qtr 08). For the period from January 1, 2012 to December 31, 2012 the cumulative return before sales charges and taxes was 7.47%.

Average Annual Total Returns for the periods ended December 31, 2012

The following table shows the average annual total returns for each class of the Fund's shares. After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes. Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for only one class and after-tax returns for other classes will vary.

Average Annual Total Returns (Oppenheimer Rochester® Limited Term Municipal Fund)		Inception Date	1 Year	5 Years (or life of class, if less)	10 Years
Class A		Nov. 11, 1986	5.05%	4.20%	4.89%
Class A Return After Taxes on Distributions			5.05%	4.20%	4.89%
Class A Return After Taxes on Distributions and Sale of Fund Shares			4.80%	4.26%	4.87%
Class B		Sep. 11, 1995	2.68%	3.65%	4.65%
Class C		Dec. 01, 1993	5.69%	3.89%	4.34%
Class Y		Jan. 31, 2011	7.82%	9.22%
Barclays Capital Municipal Bond Index			6.78%	5.91%	5.10%
Barclays Capital Municipal Bond Index (reflects no deduction for fees, expenses or taxes)	[1]			9.54%
Consumer Price Index			1.74%	1.80%	2.41%

[1] As of 01/31/2011.

XML

Expense Example (dei_DocumentInformationDocumentAxis, (Oppenheimer Rochester® Limited Term Municipal Fund), USD $)	0 Months Ended
	Jan. 28, 2013
Class A
Expense Example:
Expense Example, with Redemption, 1 Year	$ 303
Expense Example, with Redemption, 3 Years	469
Expense Example, with Redemption, 5 Years	650
Expense Example, with Redemption, 10 Years	1,173
Class B
Expense Example:
Expense Example, with Redemption, 1 Year	565
Expense Example, with Redemption, 3 Years	712
Expense Example, with Redemption, 5 Years	983
Expense Example, with Redemption, 10 Years	1,494
Class C
Expense Example:
Expense Example, with Redemption, 1 Year	259
Expense Example, with Redemption, 3 Years	493
Expense Example, with Redemption, 5 Years	851
Expense Example, with Redemption, 10 Years	1,860
Class Y
Expense Example:
Expense Example, with Redemption, 1 Year	53
Expense Example, with Redemption, 3 Years	167
Expense Example, with Redemption, 5 Years	291
Expense Example, with Redemption, 10 Years	$ 654

XML

Shareholder Fees (dei_DocumentInformationDocumentAxis, (Oppenheimer Rochester® Limited Term Municipal Fund))	0 Months Ended
	Jan. 28, 2013
Class A
Shareholder Fees:
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	2.25%
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	none
Class B
Shareholder Fees:
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	4.00%
Class C
Shareholder Fees:
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	1.00%
Class Y
Shareholder Fees:
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	none

XML

(Oppenheimer Rochester® Limited Term Municipal Fund)

Investment Objective. The Fund seeks a high level of current income exempt from federal income tax.

Fees and Expenses of the Fund. This table describes the fees and expenses that you may pay if you buy and hold or redeem shares of the Fund. You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $100,000 in certain funds in the Oppenheimer family of funds. More information about these and other discounts is available from your financial professional and in the section "About Your Account" beginning on page 15 of the prospectus and in the sections "How to Buy Shares" beginning on page 59 and "Appendix A" in the Fund's Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Oppenheimer Rochester® Limited Term Municipal Fund)	Class A	Class B	Class C	Class Y
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	2.25%	none	none	none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds)	none	4.00%	1.00%	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses (Oppenheimer Rochester® Limited Term Municipal Fund)	Class A	Class B	Class C	Class Y
Management Fees	0.41%	0.41%	0.41%	0.41%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none
Total Other Expenses	0.12%	0.20%	0.14%	0.11%
Interest and Related Expenses from Inverse Floaters	0.02%	0.02%	0.02%	0.02%
Interest and Fees from Borrowing	0.04%	0.04%	0.04%	0.04%
Other Expenses	0.06%	0.14%	0.08%	0.05%
Total Annual Fund Operating Expenses	0.78%	1.61%	1.55%	0.52%

Example. The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in a class of shares of the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your expenses would be as follows:

If shares are redeemed

Expense Example (Oppenheimer Rochester® Limited Term Municipal Fund) (USD $)	1 Year	3 Years	5 Years	10 Years
Class A	303	469	650	1,173
Class B	565	712	983	1,494
Class C	259	493	851	1,860
Class Y	53	167	291	654

If shares are not redeemed

Expense Example, No Redemption (Oppenheimer Rochester® Limited Term Municipal Fund) (USD $)	1 Year	3 Years	5 Years	10 Years
Class A	303	469	650	1,173
Class B	165	512	883	1,494
Class C	159	493	851	1,860
Class Y	53	167	291	654

Portfolio Turnover. The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 19% of the average value of its portfolio.

Principal Investment Strategies. Under normal circumstances and as a fundamental policy, the Fund invests at least 80% of its net assets (plus borrowings for investment purposes) in investment-grade municipal securities that are exempt from federal income tax (including securities subject to alternative minimum tax). Under normal market conditions and as a non-fundamental policy, the Fund will not invest more than 5% of its total assets in securities rated below-investment-grade at the time of acquisition.

Investment-grade securities are rated in one of the four highest rating categories of a nationally recognized statistical rating organization, such as Standard & Poor's (or in the case of unrated securities, determined by the Fund's investment sub-adviser to be comparable to securities rated investment-grade). The Fund also invests in unrated securities, in which case the Fund's investment sub-adviser, OppenheimerFunds, Inc., internally assigns ratings to those securities, after assessing their credit quality and other factors, in investment-grade or below-investment-grade categories similar to those of nationally recognized statistical rating organizations. There can be no assurance, nor is it intended, that the sub-adviser's credit analysis process is consistent or comparable with the credit analysis process used by a nationally recognized statistical ratings organization.

The Fund invests in municipal securities issued by the governments of states, their political subdivisions (such as cities, towns and counties), the District of Columbia, U.S. territories, commonwealths and possessions or by their agencies, instrumentalities and authorities, if the interest paid on the security is not subject to federal personal income tax (in the opinion of bond counsel to the issuer at the time the security is issued). These securities primarily include municipal bonds, municipal notes and interests in municipal leases.

The Fund seeks to maintain a dollar-weighted effective portfolio maturity of five years or less, however, it can buy securities that have short, intermediate or long maturities. Because of events affecting the bond markets and interest rate changes, the maturity of the portfolio might not meet the target at all times.

The Fund can invest substantial amounts of its assets in private activity municipal securities that pay interest that is tax-exempt but which may be a "tax-preference item" for investors subject to alternative minimum taxation. The Fund also borrows for leverage and invests in inverse floaters, a variable rate obligation and form of derivative, to seek increased income and return. The Fund can expose up to 20% of its total assets to the effects of leverage from its investments in inverse floaters. The Fund can also borrow money to purchase additional securities, another form of "leverage". Although the amount of borrowing will vary from time to time, the amount of leveraging from borrowings will not exceed one-third of the Fund's total assets.

In selecting investments for the Fund, the portfolio managers generally look for a wide range of issuers and securities nationwide that provide high current income, including unrated bonds and securities of smaller issuers that might be overlooked by other investors and funds that offer high current income. The portfolio managers also focus on securities with coupon interest or accretion rates, current market interest rates, callability and call prices that might change the effective maturity of particular securities and the overall portfolio and securities with various maturities in an effort to reduce share price volatility.

The portfolio managers may consider selling a security if any of these factors no longer applies to a security purchased for the Fund, but are not required to do so.

Principal Risks. The price of the Fund's shares can go up and down substantially. The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth more or less than what you paid for them. These risks mean that you can lose money by investing in the Fund.

Main Risks of Investing in Municipal Securities. Municipal securities may be subject to interest rate risk, credit risk, credit spread risk, extension risk, reinvestment risk and prepayment risk. Interest rate risk is the risk that when prevailing interest rates fall, the values of already-issued debt securities generally rise; and when prevailing interest rates rise, the values of already-issued debt securities generally fall, and they may be worth less than the amount the Fund paid for them. When interest rates change, the values of longer-term debt securities usually change more than the values of shorter-term debt securities. Credit risk is the risk that the issuer of a security might not make interest and principal payments on the security as they become due. If an issuer fails to pay interest or repay principal, the Fund's income or share value might be reduced. Adverse news about an issuer or a downgrade in an issuer's credit rating, for any reason, can also reduce the market value of the issuer's securities. "Credit spread" is the difference in yield between securities that is due to differences in their credit quality. There is a risk that credit spreads may increase when the market expects lower-grade bonds to default more frequently. Widening credit spreads may quickly reduce the market values of the Fund's lower-rated and unrated securities. Extension risk is the risk that an increase in interest rates could cause principal payments on a debt security to be repaid at a slower rate than expected. Extension risk is particularly prevalent for a callable security where an increase in interest rates could result in the issuer of that security choosing not to redeem the security as anticipated on the security's call date. Such a decision by the issuer could have the effect of lengthening the debt security's expected maturity, making it more vulnerable to interest rate risk and reducing its market value. Reinvestment risk is the risk that when interest rates fall the Fund may be required to reinvest the proceeds from a security's sale or redemption at a lower interest rate. Callable bonds are generally subject to greater reinvestment risk than non-callable bonds. Prepayment risk is the risk that the issuer may redeem the security prior to the expected maturity or that borrowers may repay the loans that underlie these securities more quickly than expected, thereby causing the issuer of the security to repay the principal prior to the expected maturity. The Fund may need to reinvest the proceeds at a lower interest rate, reducing its income.

Main Risks of Shorter-Term Securities. Normally, when interest rates change, the values of shorter-term debt securities change less than the values of securities with longer maturities. The Fund tries to reduce the volatility of its share prices by seeking to maintain a shorter average effective portfolio maturity. However, shorter-term securities may have lower yields than longer-term securities. Shorter-term securities are also subject to extension and reinvestment risk. The Fund is subject to extension risk when principal payments on a debt security occur at a slower rate than expected, potentially extending the average life of the security. For securities with a call date in the near future, there is the risk that an increase in interest rates could result in the issuer of that security choosing not to redeem the security as anticipated on the security's call date. Such a decision by the issuer may effectively change a short- or intermediate-term security into a longer term security, which could have the effect of locking in a below-market interest rate on the security, increasing the security's duration, making the security more vulnerable to interest rate risk, reducing the security's market value and increasing the Fund's average effective portfolio maturity. Under such circumstances, because the values of longer term securities generally fluctuate more widely in response to interest rate changes than shorter term securities, the Fund's volatility could increase. Reinvestment risk is the risk that if interest rates fall the Fund may need to invest the proceeds of redeemed securities in securities with lower interest rates.

Taxability Risk. The Fund's investments in municipal securities rely on the opinion of the issuer's bond counsel that the interest paid on those securities will not be subject to federal income tax. Tax opinions are generally provided at the time the municipal security is initially issued. However, after the Fund buys a security, the Internal Revenue Service may determine that a bond issued as tax-exempt should in fact be taxable and the Fund's dividends with respect to that bond might be subject to federal income tax.

Municipal Market Volatility and Illiquidity. The municipal bond market can be susceptible to unusual volatility, particularly for lower-rated and unrated securities. Liquidity can be reduced unpredictably in response to overall economic conditions or credit tightening. During times of reduced market liquidity, the Fund may not be able to readily sell bonds at the prices at which they are carried on the Fund's books. If the Fund needed to sell large blocks of bonds to meet shareholder redemption requests or to raise cash, those sales could further reduce the bonds' prices.

Municipal Sector Concentration. While the Fund does not invest more than 25% of its total assets in a single industry, certain types of municipal securities (such as general obligation, government appropriation, municipal leases, special assessment and special tax bonds) are not considered a part of any "industry" for purposes of this policy. Therefore, the Fund may invest more than 25% of its total assets in these types of municipal securities. These types of municipal securities may finance, or pay interest from the revenues of, projects that tend to be impacted in the same way by economic, business or political developments which would increase credit risk. For example, legislation on the financing of a project or a declining economic need for the project would likely affect all similar projects.

Special Risks of Investing in U.S. Territories, Commonwealths and Possessions. The Fund also invests in obligations of the governments of the U.S. territories, commonwealths and possessions such as the Puerto Rico, the Virgin Islands, Guam or the Northern Mariana Islands to the extent such obligations are exempt from state and/or federal income taxes, pursuant to the Fund's principal investment strategies. As applicable, these investments also are considered to be "state municipal securities" for purposes of this prospectus. Accordingly, the Fund may be adversely affected by local political and economic conditions and developments within these U.S. territories, commonwealths and possessions affecting the issuers of such obligations.

Certain of the municipalities in which the Fund invests currently experience significant financial difficulties. A credit rating downgrade relating to, default by, or insolvency or bankruptcy of, one or several municipal security issuers of a state, territory, commonwealth or possession in which the Fund invests could affect the market values and marketability of many or all municipal obligations of such state, territory, commonwealth or possession.

Risks of Land-Secured or "Dirt" Bonds. These special assessment or special tax bonds are issued to promote residential, commercial or industrial growth and redevelopment. They are exposed to real estate development-related risks. The bonds could default if the developments failed to progress as anticipated or if taxpayers failed to pay the assessments, fees and taxes specified in the financing plans for a project.

Risks of Tobacco Related Bonds. In 1998, the largest U.S. tobacco manufacturers reached an out of court agreement, known as the Master Settlement Agreement (the "MSA"), to settle claims against them by 46 states and six other U.S. jurisdictions. The tobacco manufacturers agreed to make annual payments to the government entities in exchange for the release of all litigation claims. A number of the states have sold bonds that are backed by those future payments. The Fund may invest in two types of those bonds: (i) bonds that make payments only from a state's interest in the MSA and (ii) bonds that make payments from both the MSA revenue and from an "appropriation pledge" by the state. An "appropriation pledge" requires the state to pass a specific periodic appropriation to make the payments and is generally not an unconditional guarantee of payment by a state.

The settlement payments are based on factors, including, but not limited to, annual domestic cigarette shipments, cigarette consumption, inflation and the financial capability of participating tobacco companies. Payments could be reduced if consumption decreases, if market share is lost to non-MSA manufacturers, or if there is a negative outcome in litigation regarding the MSA, including challenges by participating tobacco manufacturers regarding the amount of annual payments owed under the MSA.

The Fund can invest up to 25% of its total assets in tobacco-related bonds without an appropriation pledge that make payments only from a state's interest in the MSA.

Main Risks of Borrowing and Leverage. The Fund can borrow up to one-third of the value of its total assets (including the amount borrowed) from banks, as permitted by the Investment Company Act of 1940. It can use those borrowings for a number of purposes, including for purchasing securities, which can create "leverage." In that case, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not borrow. Borrowing results in interest payments to the lenders and related expenses. Borrowing for investment purposes might reduce the Fund's return if the yield on the securities purchased is less than those borrowing costs. The Fund may also borrow to meet redemption obligations, for temporary and emergency purposes, or to unwind or contribute to trusts in connection with the Fund's investment in inverse floaters (instruments also involving the use of leverage, as discussed below). The Fund currently participates in a line of credit with other Oppenheimer funds for its borrowing.

The Fund can participate in a committed reverse repurchase agreement program. Reverse repurchase agreements that the Fund may engage in also create leverage. A reverse repurchase agreement is the sale by the Fund of a debt obligation to a party for a specified price, with the simultaneous agreement by the Fund to repurchase that debt obligation from that party on a future date at a higher price. Similar to a borrowing, reverse repurchase agreements provide the Fund with cash for investment and operational purposes. When the Fund engages in reverse repurchase agreements, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not engage in these transactions due to the effect of leverage. Reverse repurchase agreements create fund expenses and require that the Fund have sufficient cash available to repurchase the debt obligation when required. Reverse repurchase agreements also involve the risk that the market value of the debt obligation that is the subject of the reverse repurchase agreement could decline significantly below the price at which the Fund is obligated to repurchase the security.

Risks of Derivatives. A "derivative" is an investment whose value depends on (or is derived from) the value of an underlying security, asset, interest rate, index or currency. Derivatives may be volatile and involve significant risks. Derivative transactions may require the payment of premiums and can increase portfolio turnover. Certain derivative investments may be illiquid. The underlying security or other reference on which a derivative is based, or the derivative itself, may not perform the way the Fund expects it to. The Fund could realize little or no income or lose principal from a derivative investment or a hedge might be unsuccessful. The Fund may also lose money if the issuer of a derivative fails to pay the amount due.

Inverse Floaters. The Fund invests in inverse floating rate securities ("inverse floaters") because, under ordinary circumstances, they offer higher yields and thus provide higher income than fixed-rate municipal bonds of comparable maturity and credit quality. Because inverse floaters are leveraged instruments, the value of an inverse floater will change more significantly in response to changes in interest rates and other market fluctuations than the market value of a conventional fixed-rate municipal security of comparable maturity and credit quality, including the municipal bond underlying an inverse floater.

An inverse floater is created when a fixed-rate municipal bond is contributed to a trust. The trust issues two separate classes of securities: short-term floating rate securities with a fixed principal amount that represent a senior interest in the underlying municipal bond, and the inverse floater that represents a residual, subordinate interest in the underlying municipal bond. The trust issues and sells the short-term floating rate securities to third parties and the inverse floater to the Fund. The short-term floating rate securities generally bear short-term rates of interest. When interest is paid on the underlying municipal bond to the trust, such proceeds are first used to pay interest owing to holders of the short-term floating rate securities, with any remaining amounts being paid to the Fund, as the holder of the inverse floater. Accordingly, the amount of such interest paid to the Fund is inversely related to the rate of interest on the short-term floating rate securities. Inverse floaters produce less income when short-term interest rates rise (and, in extreme cases, may pay no income) and more income when short-term interest rates fall. Thus, if short-term interest rates rise after the issuance of the inverse floater, any yield advantage to the Fund is reduced and may be eliminated. Additionally, because the principal amount of the short-term floating rate security is fixed and is not adjusted in response to changes in the market value of the underlying municipal bond, any change in the market value of the underlying municipal bond is reflected entirely in a change to the value of the inverse floater. Upon the occurrence of certain adverse events, a trust may be collapsed and the underlying municipal bond liquidated, and the Fund could lose the entire amount of its investment in the inverse floater and may, in some cases, be contractually required to pay the negative difference, if any, between the liquidation value of the underlying municipal bond and the principal amount of the short-term floating rate securities.

The Fund may invest in inverse floaters with any degree of leverage (measured by comparing the outstanding principal amount of related short-term floating rate securities to the par value of the underlying municipal bond). However, the Fund may only expose up to 20% of its total assets to the effects of leverage from its investments in inverse floaters. This limitation is measured by comparing the aggregate principal amount of the short-term floating rate securities that are related to the inverse floaters held by the Fund to the total assets of the Fund. Nevertheless, the value of, and income earned on, an inverse floater that has a higher degree of leverage (represented by a larger outstanding principal amount of related short-term floating rate securities) will fluctuate more significantly in response to changes in interest rates and to changes in the market value of the related underlying municipal bond, and are more likely to be eliminated entirely under adverse market conditions.

Who Is the Fund Designed For? The Fund is designed for investors seeking a high level of current income exempt from federal income tax. Due to the Fund's emphasis on investment-grade securities and an intermediate effective average maturity intended to reduce overall portfolio volatility, the Fund's yield may be lower than longer-term municipal bond funds or municipal bond funds that can invest more of their assets in lower-grade investments. Because it invests in tax-exempt securities, the Fund is not appropriate for a retirement plan or other tax-exempt or tax-deferred account. The Fund is not a complete investment program. You should carefully consider your own investment goals and risk tolerance before investing in the Fund.

An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

The Fund's Past Performance. The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance (for Class A shares) from year to year and by showing how the Fund's average annual returns for 1, 5 and 10 years compare with those of a broad measure of market performance. The Fund's past investment performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. More recent performance information is available by calling the toll-free number on the back of this prospectus and on the Fund's website: https://www.oppenheimerfunds.com/fund/LimitedTermMunicipalFund

Sales charges and taxes are not included and the returns would be lower if they were. During the period shown, the highest return for a calendar quarter was 7.00% (3rd Qtr 09) and the lowest return was -10.29% (4th Qtr 08). For the period from January 1, 2012 to December 31, 2012 the cumulative return before sales charges and taxes was 7.47%.

Average Annual Total Returns for the periods ended December 31, 2012

The following table shows the average annual total returns for each class of the Fund's shares. After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes. Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for only one class and after-tax returns for other classes will vary.

Average Annual Total Returns (Oppenheimer Rochester® Limited Term Municipal Fund)		Inception Date	1 Year	5 Years (or life of class, if less)	10 Years
Class A		Nov. 11, 1986	5.05%	4.20%	4.89%
Class A Return After Taxes on Distributions			5.05%	4.20%	4.89%
Class A Return After Taxes on Distributions and Sale of Fund Shares			4.80%	4.26%	4.87%
Class B		Sep. 11, 1995	2.68%	3.65%	4.65%
Class C		Dec. 01, 1993	5.69%	3.89%	4.34%
Class Y		Jan. 31, 2011	7.82%	9.22%
Barclays Capital Municipal Bond Index			6.78%	5.91%	5.10%
Barclays Capital Municipal Bond Index (reflects no deduction for fees, expenses or taxes)	[1]			9.54%
Consumer Price Index			1.74%	1.80%	2.41%

[1] As of 01/31/2011.