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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-05-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001018187</rptOwnerCik>
            <rptOwnerName>GRIFFITHS SCOTT A</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>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2014-05-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3246</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>36046</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares of restricted stock granted on May 1, 2014 under the issuer's Board Compensation Program and 2009 Long Term Incentive Plan, each as amended.  The restricted shares are subject to customary transfer restrictions and risk of forfeiture provisions, one-half of which lapse immediately on the transaction date and one-half on the day preceding the date of the next annual meeting of stockholders.</footnote>
        <footnote id="F2">Consistent with the provisions of the Issuer's 2009 Long Term Incentive Plan, the grantee did not pay any consideration to the Issuer for the restricted shares that were granted.  By way of reference, the closing price per share of the Issuer's common stock on the New York Stock Exchange on May 1, 2014 was $38.51.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>David Cedro, Attorney in Fact</signatureName>
        <signatureDate>2014-05-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
