Preheat oven to 350. Butter a 9×13 baking dish. In a skillet over high heat, cook and crumble the sausage. Add the onion and diced bell pepper and cook until vegetables are soft, about 6-8 minutes. Scatter the sausage vegetable mixture into the baking dish. In a large bowl, whisk together the milk and eggs. Season with salt and pepper, then pour over the sausage and vegetables. Sprinkle with the cheese, then arrange the tater tots neatly in a single layer over the eggs. Bake until eggs are set and tots are crisp on top, about 40-45 minutes. If desired, turn on the broiler for a couple of minutes at the end to crisp up the potatoes.