1. Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Sauté onions until softened and starting to brown, about 6 min. Add peppers and mushrooms and cook until vegetable mixture is tender, about another 6-8 minutes more. Transfer mixture to a bowl.
2. Meanwhile, slice steak very thinly and season with salt (in moderation) and pepper. Heat remaining oil in skillet and cook steak slices until browned and cooked through, about 4–5 minutes.
3. Top each dinner roll with meat, a piece of cheese and some of the vegetable mixture. Serve while warm.
Per serving: 302 calories, 14g fat, 5g saturated fat, 46mg cholesterol, 375mg sodium, 26g carbohydrate, 2g fiber, 6g sugar, 19g protein