Anywhere in Western, northwestern, or the panhandle of Oklahoma will normally produce quite a few birds. Far northwestern and the panhandle will also give you a good oppurtunity to harvest pheasant and Blue (scaled) quail along with the bobwhites. There are several areas of public land and sometimes it isn't that hard to hunt private land if you just ask landowners in the area. Here is a link to the public land areas in Oklahoma.
http://129.15.97.32/odwcims/
This website contains the seasons, regulations, and numerous other things related to Oklahoma wildlife and outdoors.
www.wildlifedepartment.com
Hope this helps,
Trent