Right on the oatmeal; it's Bob's Red Mill, and it's very small crumbs; nothing at all like our rolled oats. The only concern I have about adding oatmeal to bulk up the cookies is how long it takes to cook, since stone-ground or steel cut oats are still essentially raw, you might end up with chewy little bits of oat when the rest of your ingredients have seen enough heat. "Quick" oats might work pretty well though.