Oklahoma and Arkansas do both take some OOS students, but they heavily favor ISers.
You know how Texas schools must take 90% IS students? Arkansas goes one step farther- they have to take a certain proportion from each of several regions in the state. They also only have ONE OOS interview day.
From personal experience, unless you have very high numbers AND strong ties to the state, it is useless to apply to OU. I have strong ties and I was given their last interview date, which was February 5th. By that time I had matched at Houston, so I withdrew from OU... who wants to pay estimated COA $51,000/yr as an OOSer anyhow.... ouch.