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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-06-03</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000750199</issuerCik>
        <issuerName>EPL OIL &amp; GAS, INC.</issuerName>
        <issuerTradingSymbol>EPL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001519687</rptOwnerCik>
            <rptOwnerName>Jensen W Mac</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O EPL OIL &amp; GAS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>919 MILAM STREET, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP, Business Development</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2014-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25385</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9844</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <transactionDate>
                <value>2014-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>9844</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>39.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2014-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>20.6516</value>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2014-06-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>42334</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>18.3484</value>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>42334</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On June 3, 2014, EPL Oil &amp; Gas, Inc. (the &quot;Issuer&quot;) became an indirect wholly?owned subsidiary of Energy XXI (Bermuda) Limited (&quot;EXXI&quot;), as a result of the merger of Clyde Merger Sub, Inc. (&quot;Merger Sub&quot;), a wholly-owned subsidiary of Energy XXI Gulf Coast, Inc., an indirect wholly owned subsidiary of Energy XXI (&quot;OpCo&quot;), with and into EPL (the &quot;Merger&quot;). The Merger was effected pursuant to an Agreement and Plan of Merger, dated as of March 12, 2014, by and among EXXI, EPL, OpCo and Merger Sub (as amended, the &quot;Merger Agreement&quot;).  Under the Merger Agreement, at the effective time of the Merger, each outstanding restricted share of EPL Common Stock fully vested at the Effective Time and was treated as a share of EPL Common Stock for all purposes of the Merger Agreement, including the right to receive the merger consideration.</footnote>
        <footnote id="F2">Based on the Cash Election made by the Reporting Person with respect to the form of merger consideration to be received in the Merger, the Reporting Person's shares of Common Stock of the Issuer were converted in the Merger into the right to receive a combination of (a) $25.92 in cash (without interest) and 0.5595 of a share of EXXI Common Stock.  The closing price for EXXI Common Stock on the NASDAQ Capital Market for June 3, 2014 was $21.11 per share.</footnote>
        <footnote id="F3">Pursuant to the Reporting Person's Rule 10b5-1 plan, the Issuer withheld shares of Common Stock from the Reporting Person to pay the withholding tax obligations related to the lapse of transfer and forfeiture restrictions on restricted shares of Common Stock held by the Reporting Person.</footnote>
        <footnote id="F4">The Reporting Person disclaims any beneficial ownership of the 100 shares of common stock owned by his spouse.</footnote>
        <footnote id="F5">The exercise price reflects the weighted average exercise price for the Reporting Person's outstanding stock options, which were scheduled to expire on dates ranging from May 2, 2021 to January 6, 2024.</footnote>
        <footnote id="F6">Under the Merger Agreement, at the effective time, each stock option to purchase shares of EPL Common Stock became fully vested and was converted into the right to receive (a) $39.00 multiplied by (b) the excess of $39.00 over the exercise price for such stock option.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>David Cedro, Attorney in Fact</signatureName>
        <signatureDate>2014-06-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
