Okla. Stat. tit. 42, § 171

All claims for liens and rights of action to recover therefor hereunder shall be assignable so as to vest in the assignee all rights and remedies herein given, subject to all defenses thereto that might be made if such assignment had not been made. Where a statement has been filed and recorded as provided in Section 142 of this title, such assignment may be made by an entry, on the same page of the mechanics' lien journal containing the record of the lien, signed by the claimant or his lawful representative, and attested by the county clerk; or such assignment may be made by a separate instrument in writing.