Preheat oven to 375 degrees.
Prepare macaroni and cheese according to directions on box. Grease a 13x9-inch baking dish. Add the beaten eggs to macaroni and cheese and mix well. Spread in the baking dish and bake at 375 degrees for 10 minutes. Remove and set aside.
Mix tomato sauce, onion, green pepper and oregano. Spoon evenly over macaroni and cheese mixture. Then add pepperoni slices and mozzarella cheese. Bake at 375 degrees for 15 to 25 minutes more; slice and serve. Serves 8 slices.