Preheat the oven to 350 degrees (if baking immediately). Spray a 9x13 inch baking dish with cooking spray.
In the prepared dish, add the hashbrowns, cooked sausage, onions, bell peppers, and 1 1/2 cups of cheese. Gently mix the ingredients together and spread evenly in the dish.
In a large bowl, add the eggs, milk, salt and pepper. Whisk until well combined.
Pour the egg mixture over the hashbrown mixture and sprinkle the remaining cheese over top.
Cover the dish with foil and refrigerate overnight if desired, or bake immediately.
Bake covered for 55-65 minutes or until cooked through.