Well, a mash is kind of like a steep, so if you put the oats in with some grain, and hold it at 150 degrees for 45 minutes, that's a mash. It's confusing, I know!
Could you post the recipe you're thinking of, and we'll see how it looks. It'll be alot easier to do that, rather than giving you general advice that might be wrong! We can see exactly what you'd need to do.
Broken Leg Brewery
Giving beer a leg to stand on since 2006