Heres a link with a list of legal orv areas on oklahoma:
You're not too far from little sahara or you could go east and head to keystone lake. Keystone is pretty much a straight shot down 412 from there. Look for appalachia bay or white water park. White water is a good spot for sand and mud (beware the water holes there, they're basically quicksand at the bottom).
Theres a lot of trails that can be done in the area that are closer to you, but not on any official list I hear, but since I live in the northeast im not familiar with em. Best bet is to google some local 4-wheel clubs and get in contact with them for the unnofficial riding areas.