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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-03-10</periodOfReport>

    <issuer>
        <issuerCik>0001004980</issuerCik>
        <issuerName>PG&amp;E CORP</issuerName>
        <issuerTradingSymbol>PCG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001221221</rptOwnerCik>
            <rptOwnerName>RAMBO BARBARA L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PG&amp;E CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>ONE MARKET, SPEAR TOWER, SUITE 2400</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-03-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1054</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>11362.34</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-03-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1054.11</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12416.45</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Restricted shares granted under the PG&amp;E Corporation 2006 Long-Term Incentive Plan (LTIP).</footnote>
        <footnote id="F2">Restricted Stock Units (RSUs) granted under the PG&amp;E Corporation 2006 LTIP.  RSUs are payable in shares of PG&amp;E Corporation common stock on a one-for-one basis upon a director's death, disability, retirement, or a change in control, as defined in the PG&amp;E Corporation 2006 LTIP.</footnote>
        <footnote id="F3">This total includes 1088.25 units of phantom stock granted under the PG&amp;E Corporation Non-Employee Director Stock Incentive Plan (SIP), and reflects the acquisition of 11.59 units of phantom stock on 4/15/09, 11.69 units of phantom stock on 7/15/09, 10.61 units of phantom stock on 10/15/09, and 10.06 units of phantom stock on 1/15/10, pursuant to a dividend reinvestment feature of the SIP.  This total also includes 5,399.17 RSUs granted under the LTIP, and reflects the acquisition of 46.27 RSUs on 4/15/09, 46.69 RSUs on 7/15/09, 42.36 RSUs on 10/15/09, and 40.17 RSUs on 1/15/10, pursuant to a dividend reinvestment feature of the LTIP.  The phantom stock units and the RSUs are automatically payable in shares of PG&amp;E Corporation common stock only.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Eric A. Montizambert, attorney-in-fact for Barbara L. Rambo (signed Power of Attorney on file with SEC)</signatureName>
        <signatureDate>2010-03-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
