Preheat oven to 375 degrees F.Butter a 13" x 9" baking dish. Set aside.Place potatoes in a large mixing bowl.In a large skillet, cook bacon until almost all pieces are crispy. Add sausage and cook until done.Add garlic and all diced veggies (onion, peppers and mushrooms). Cook until onions are translucent.Add the sausage veggie mixture and half of cheese to potatoes and stir in gently. Spread the mixture in prepared baking dish.In a large measuring cup or small bowl, whisk together eggs and milk. Add salt and pepper and whisk together.Pour the egg mixture over potatoes.Sprinkle remaining cheese over the top.Bake for 40 to 43 minutes or until sizzling and the cheese is melted.Let stand 10 to 15 minutes before serving.