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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 9yptFV3KZg9wRMPjNhE/WA==

<SEC-DOCUMENT>0001104659-09-061969.txt : 20091102
<SEC-HEADER>0001104659-09-061969.hdr.sgml : 20091102
<ACCEPTANCE-DATETIME>20091102211914
ACCESSION NUMBER:		0001104659-09-061969
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091102
FILED AS OF DATE:		20091102
DATE AS OF CHANGE:		20091102

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ogilvie Marran H.
		CENTRAL INDEX KEY:			0001474850

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34516
		FILM NUMBER:		091152541

	MAIL ADDRESS:	
		STREET 1:		599 LEXINGTON AVENUE
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10022

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COWEN GROUP, INC.
		CENTRAL INDEX KEY:			0001466538
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY BROKERS, DEALERS & FLOTATION COMPANIES [6211]
		IRS NUMBER:				000000000

	BUSINESS ADDRESS:	
		STREET 1:		1221 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10020
		BUSINESS PHONE:		(646) 562-1000

	MAIL ADDRESS:	
		STREET 1:		1221 AVENUE OF THE AMERICAS
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10020

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	LexingtonPark Parent Corp
		DATE OF NAME CHANGE:	20090617
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-11-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001466538</issuerCik>
        <issuerName>COWEN GROUP, INC.</issuerName>
        <issuerTradingSymbol>COWN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001474850</rptOwnerCik>
            <rptOwnerName>Ogilvie Marran H.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O COWEN GROUP, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>599 LEXINGTON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Partner Managing Director</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-11-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>307233</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>307233</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Upon consummation of the transactions (the &quot;Transactions&quot;) contemplated by the Transaction Agreement and Agreement and Plan of Merger, dated as of June 3, 2009, by and among Cowen Holdings, Inc. (f/k/a Cowen Group, Inc.), Cowen Group, Inc. (f/k/a/ LexingtonPark Parent Corp.), Lexington Merger Corp., Ramius LLC (f/k/a Park Exchange LLC) and RCG Holdings LLC (f/k/a Ramius LLC) (&quot;RCG&quot;), 37,536,826 shares of Class A Common Stock were issued to RCG.  The Reporting Person is a member of RCG and may be deemed to have a pecuniary interest in 307,233 shares of Class A Common Stock that were acquired by RCG in the Transactions.  The Reporting Person's acquisition of a pecuniary interest in these shares was pursuant to an exempt transaction pursuant to Rule 16b-3 under the Securities Exchange Act of 1934, as amended.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Marran H. Ogilvie</signatureName>
        <signatureDate>2009-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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