Preheat oven to 350°F and lightly grease a 9×13 pan.
Place the hash browns, cooked sausage, onions, bell peppers, and 2 cups of cheese in a large bowl. Gently mix the ingredients together and spread evenly in the 9×13 pan.
Combine the eggs, milk, salt, and pepper in a bowl. Whisk until well combined.
Pour the egg mixture over the hash brown mixture and sprinkle the remaining cup of cheese evenly on top.
Bake uncovered for 55-65 minutes or until cooked through and bubbly around the edges.
