If anyone's ever in OKC, just PM me. I can give you a basically exhaustive list of what's good here (at least in the downtown/inner-city area) and I've been to 'em all.
One place we send a lot of clients is the Paseo Grille located in OKC's Paseo Arts District.
It's a neat little area right in the middle of a historic neighborhood. The architecture is sort of Santa-Fe-ish. There are a lot of art studios, a couple of restaurants, etc. I don't think any tourists really know about the area, and it's really surprising that it is where it is.
At any rate, the restaurant is amazingly good. Also, they have an excellent scotch menu.