-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 Snlb7wo8iGH+RLaF+gSu29lgvW9/Xcmg+QG7Ed8ESOJDuZo9WvcXk4/5ZZIurEy2
 yCbGAzzf09eP8Rod+qT99g==

<SEC-DOCUMENT>0000895126-07-000178.txt : 20070525
<SEC-HEADER>0000895126-07-000178.hdr.sgml : 20070525
<ACCEPTANCE-DATETIME>20070525164814
ACCESSION NUMBER:		0000895126-07-000178
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070523
FILED AS OF DATE:		20070525
DATE AS OF CHANGE:		20070525

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			GASTAR EXPLORATION LTD
		CENTRAL INDEX KEY:			0001170154
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				383324634
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1331 LAMAR STREET
		STREET 2:		SUITE 1080
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77010
		BUSINESS PHONE:		7137391800

	MAIL ADDRESS:	
		STREET 1:		1331 LAMAR STREET
		STREET 2:		SUITE 1080
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77010

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CHESAPEAKE ENERGY CORP
		CENTRAL INDEX KEY:			0000895126
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		STATE OF INCORPORATION:			OK
		FISCAL YEAR END:			0407

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32714
		FILM NUMBER:		07881174

	BUSINESS ADDRESS:	
		STREET 1:		6100 N WESTERN AVE
		CITY:			OKLAHOMA CITY
		STATE:			OK
		ZIP:			73118
		BUSINESS PHONE:		4058488000

	MAIL ADDRESS:	
		STREET 1:		6100 NORTH WESTERN AVE
		CITY:			OKLAHOMA CITY
		STATE:			OK
		ZIP:			73118
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-05-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001170154</issuerCik>
        <issuerName>GASTAR EXPLORATION LTD</issuerName>
        <issuerTradingSymbol>gst</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000895126</rptOwnerCik>
            <rptOwnerName>CHESAPEAKE ENERGY CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6100 NORTH WESTERN AVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>OKLAHOMA CITY</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>73118</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-05-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1757195</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33908836</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Jennifer M. Grigsby</signatureName>
        <signatureDate>2007-05-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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