It depends on your stats and how strong your ties are, honestly. OU is required to accept at least 75% of applicants from in-state. That puts OOS applicants at a numbers disadvantage already, but it's not impossible--there are several people in my class not from Oklahoma.
One of the biggest things our adcoms want to see is that you hopefully want to stay and practice in Oklahoma. I once heard a ridiculous number for the amount of money it takes to train each student, which I'm not sure is true or not. However, the whole point of making the admissions process so IS-friendly is so that OU can crank out physicians that have a strong enough tie to Oklahoma to eventually settle there and continue their careers in the long run.
I wouldn't advise you, or anyone else for that matter, not to apply as an OOS student. But if you do, keep in mind that you'll most likely be asked in your interview (directly or indirectly) what makes you want to come to Oklahoma, and if you could see yourself practicing here long term. A positive response (and genuine response) would hopefully give you an edge over someone just applying for the hell of it, if that makes sense.