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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-02-07</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001512471</rptOwnerCik>
            <rptOwnerName>Broussard Andre J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O EPL OIL &amp; GAS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>919 MILAM, SUITE 1600</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP - Geosciences</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2013-02-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>545</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.37</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>31494</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">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>
    </footnotes>

    <ownerSignature>
        <signatureName>David Cedro, Attorney in Fact</signatureName>
        <signatureDate>2013-02-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
