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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-04-30</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001263376</rptOwnerCik>
            <rptOwnerName>BUCKNER CHARLES OLIVER</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O EPL OIL &amp; GAS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>201 ST. CHARLES AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW ORLEANS</rptOwnerCity>
            <rptOwnerState>LA</rptOwnerState>
            <rptOwnerZipCode>70170</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2013-04-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>3061</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>32800</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares of restricted stock granted on April 30, 2013 under the issuer's Board Compensation Program and 2009 Long Term Incentive Plan, each as amended.  Under the terms of the issuer's Second Amended and Restated Stock and Deferral Plan for Non-Employee Directors, as amended, receipt of these shares has been deferred by the reporting person.  Accordingly, the deferred shares will be delivered to the reporting person in a lump sum payable on the date the reporting person ceases his service as a director.</footnote>
        <footnote id="F2">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="F3">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 April 30, 2013 was $32.67.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>David Cedro, Attorney in Fact</signatureName>
        <signatureDate>2013-05-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
