Okla. Stat. tit. 74, § 1369

A. A state employee shall be eligible to participate in the plan commencing July 1 of the plan year beginning July 1, 2001, and commencing January 1 for any plan year beginning after January 1, 2002, provided such employee qualifies as a participant as provided in this act. B. Except to the extent a benefit plan provides otherwise, each participant's eligibility to participate in the plan and each benefit plan shall terminate on the participant's termination. C. Each of the benefit plans incorporated in the plan may have its own eligibility requirements for participation which differ from those set forth in the plan to govern participation in the plan. The eligibility requirements set forth in the plan relate only to participation in the plan and shall have no effect on such eligibility requirements.