Yes. I've been giving my birds straight oats for a month now. I've added game bird chow as a supplement and mixed it in with the oats. I'm working on switching them to Game Bird Chow completely however. I needed more protein for my showbirds.
Alot of people mix their own feeds using whole oats, barley, wheat, and other grains. Especially the organic minded folks.
HOWEVER, when feeding whole grains, you HAVE to feed them free choice granite grit. They need SHARP edged grit to help digest the grains.