<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-12-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000316300</issuerCik>
        <issuerName>EXCO RESOURCES INC</issuerName>
        <issuerTradingSymbol>XCO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001189523</rptOwnerCik>
            <rptOwnerName>ARES CORPORATE OPPORTUNITIES FUND LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001395111</rptOwnerCik>
            <rptOwnerName>ACOF EXCO, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001395112</rptOwnerCik>
            <rptOwnerName>ACOF EXCO 892 Investors, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001230743</rptOwnerCik>
            <rptOwnerName>ACOF MANAGEMENT LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001259315</rptOwnerCik>
            <rptOwnerName>ACOF OPERATING MANAGER LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001371903</rptOwnerCik>
            <rptOwnerName>Ares Corporate Opportunities Fund II, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001395110</rptOwnerCik>
            <rptOwnerName>Ares EXCO, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001395109</rptOwnerCik>
            <rptOwnerName>Ares EXCO 892 Investors, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001372044</rptOwnerCik>
            <rptOwnerName>ACOF Management II, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ARES MANAGEMENT LLC</rptOwnerStreet1>
            <rptOwnerStreet2>2000 AVENUE OF THE STARS, 12TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2008-12-02</value>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>9100</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.70</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12212162</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This Form 4 is filed jointly by Ares Corporate Opportunities Fund, L.P. (&quot;ACOF&quot;), ACOF EXCO, L.P. (&quot;ACOF EXCO&quot;), ACOF EXCO 892 Investors, L.P. (&quot;ACOF 892&quot;), ACOF Management L.P. (&quot;ACOF Management&quot;), ACOF Operating Manager, L.P. (&quot;ACOF Operating&quot;), Ares Corporate Opportunities Fund II, L.P. (&quot;ACOF II&quot;), Ares EXCO, L.P. (&quot;Ares EXCO&quot;), Ares EXCO 892 Investors, L.P. (&quot;Ares 892&quot;), ACOF Management II, L.P. (&quot;ACOF Management II&quot;), ACOF Operating Manager II, L.P. (&quot;ACOF Operating II&quot;), Ares Management LLC (&quot;Ares Management&quot;) and Ares Partners Management Company, LLC (&quot;Ares Partners&quot; and, collectively the &quot;Ares Entities&quot;).</footnote>
        <footnote id="F2">On December 2, 2008, ACOF purchased 9,100 shares of common stock, par value $0.001 per share (&quot;Common Stock&quot;) of EXCO Resources, Inc. (the &quot;Issuer&quot;) in an open market transaction at a price per share of $6.70.</footnote>
        <footnote id="F3">This amount includes 25,000 shares of Common Stock, which represents the vested portion of stock options to acquire 50,000 shares of Common Stock which were issued to Jeffrey S. Serota as an initial grant pursuant to the Amended and Restated 2007 Director Plan of the Issuer upon becoming one of the directors of the Issuer in March 2007.</footnote>
        <footnote id="F4">Mr. Serota is a Partner in the Private Equity Group of Ares Management, which indirectly controls each of ACOF, ACOF EXCO, ACOF 892, ACOF II, Ares EXCO and Ares 892 each of which is a record holder of Common Stock. These stock options are held by Mr. Serota for the benefit of the Ares Entities and Mr. Serota has assigned all economic, pecuniary and voting rights in respect of these stock options to the Ares Entities. Mr. Serota disclaims beneficial ownership of these stock options and the securities held by the Ares Entities, except to the extent of any pecuniary interest therein.</footnote>
        <footnote id="F5">The general partner of each of ACOF, ACOF EXCO and ACOF 892 is ACOF Management and the general partner of ACOF Management is ACOF Operating Manager. The general partner of each of ACOF II, Ares EXCO and Ares 892 is ACOF Management II and the general partner of ACOF Management II is ACOF Operating Manager II. Each of ACOF Operating Manager and ACOF Operating Manager II are indirectly owned by Ares Management which, in turn, is indirectly controlled by Ares Partners. Anthony P. Ressler is the Manager of Ares Partners. Each of Mr. Ressler, the Ares Entities and the partners, members and managers thereof (other than ACOF, ACOF EXCO, ACOF 892, ACOF II, Ares EXCO and Ares 892, in each case with respect to the shares owned of record by such entity) disclaims beneficial ownership of these shares of Common Stock, except to the extent of any pecuniary interest therein. The address of each Ares Entity is 2000 Avenue of the Stars, 12th Floor, Los Angeles, CA 90067.</footnote>
        <footnote id="F6">The filing of this Form 4 shall not be deemed an admission that any such person or entity is the beneficial owner or has pecuniary interest in, any such securities for purposes of Section 16 of the Securities Exchange Act of 1934, or for any other purpose.</footnote>
    </footnotes>

    <remarks>Additional Reporting Persons: (i) ACOF Operating Manager II, L.P. (Relationship to the Issuer: Director), c/o Ares Management LLC, 2000 Avenue of the Stars, 12th Floor, Los Angeles, CA 90067; (ii) Ares Management LLC (Relationship to the Issuer: Director), 2000 Avenue of the Stars, 12th Floor, Los Angeles, CA 90067; and (iii) Ares Partners Management Company LLC (Relationship to the Issuer: Director), c/o Ares Management LLC, 2000 Avenue of the Stars, 12th Floor, Los Angeles, CA 90067.</remarks>

    <ownerSignature>
        <signatureName>See signatures attached as Exhibit 99.1</signatureName>
        <signatureDate>2008-12-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
