D&D family of Games in Norman, Oklahoma
Your problem is really that the Oklahoma gaming community is rather insular-there are many groups but most are small groups of friends that don't really advertise they play to other folks.
I know folks in Norman, Oklahoma, that run 3.5 D&D.  Those I know most closely aren't really consistent on running the game, so that's probably not what you want.
I know that some of the folks who frequent my friendly local game store, Wizard's Games, play 3.5  D&D consistently.  The store's website is 
www.wizards-games.com or the phone is (405) 292-GAME   Try looking at the bulletin board there for a game, or if you want to GM, the owner (Brian) will let you post a notice on the board.
If you ever want to play 4th edition, we have a vibrant HackMaster group in Norman and I am thinking about starting a low-key HackMaster game set in the Kingdoms of Kalamar setting (which is 3/3.5) that will run at Wizard's Asylum.  I have some legwork to do but would know in about a week what day I'd run said game if it happens.
Good luck finding a game!