Okla. Stat. tit. 18, § 18-438.11
Waiver of notice of meeting
Any person entitled to notice of a meeting may waive such notice
in writing either before or after such meeting. If any such person
shall attend such meeting, such attendance shall constitute a waiver
of notice of such meeting, unless such person participates therein
solely to object to the transaction of any business because the
meeting has not been legally called or convened.