I generally use a pound and a half of oatmeal in my O.Stout. I use traditional flaked oats from quaker, not quick oats. Though it might not matter much. I like to use 1.5lbs (24oz). I toast half a pound of them in the oven.
Oatmeal doesn't really taste like much, but judges seem to think it does.
So look to somewhere else in your grain bill to help out. I'd add a little biscuit or victory malt (0.5lb). And also bump up your chocolate malt slightly too if you are using any.
These two things will help increase the desire to have some nutty, toasty flavors.