If you have not heard of Crossbar Ranch, you need to check it out. It is located about 20 miles north of Ardmore and 60 miles south of OKC.
The ranch totals about 6,500 acres. So far they have 2 big loops with many cut through trails. The south loop is great for less experienced riders and the north loop is pretty tricked up. I have heard they have about 70 miles of total trails. They continue to cut new ones. It is an interesting concept because the city of Davis is behind the development of this off road riding area.
Google Crossbar Ranch and you should find all the information you need. Definitely worth a trip for a day trip or the weekend.