Grease a 3-quart casserole and line with bread cubes. Sprinkle with cheese.
Mix eggs, milk, dry mustard, salt, onion powder and pepper. Pour evenly over the bread and cheese. Sprinkle sausage, mushrooms and tomatoes on top of the casserole. Cover and refrigerate overnight.
Preheat oven to 325° F.
Bake uncovered approximately 1 hour. Serve hot.Servings: 8