My personal recipe: Microwave oats in an 8x8 Pyrex for 2 minutes, then bake for 1 hour at 180 degrees.
I don't think there's any perfect answer, just one that assures that the mites don't survive but the oatmeal stays as close to uncooked oatmeal as possible.
By the way, I also like oatmeal versus bran. I've found that if I can keep oats reasonably dry, I can keep using it versus throwing it out like you would with bran.