Okla. Stat. tit. 41, § 111

agree.
E. The written notice, required by the Oklahoma Residential
Landlord and Tenant Act, to terminate any tenancy shall be served on
the tenant or landlord personally unless otherwise specified by law.
If the tenant cannot be located, service shall be made by delivering
the notice to any family member of such tenant over the age of
twelve (12) years residing with the tenant. If service cannot be