Okla. Stat. tit. 74, § 1226.11

Bonds issued under the provisions of this act are hereby made securities in which all public officers and public bodies, agencies, and instrumentalities of the state and its political subdivisions, all banks, trust companies, trust and loan associations, investment companies, and others carrying on a banking business, and all insurance companies and insurance associations, and others carrying on an insurance business, may legally and properly invest funds including capital in their control or belonging to them.