Preheat the oven to 350°F. Grease a 9x13-inch baking dish with cooking spray or butter.
In a large bowl, combine the thawed hashbrowns, cooked sausage, bell peppers, and onion. Spread this mixture evenly in the prepared baking dish.
In another bowl, whisk together the eggs, milk, garlic powder, onion powder, salt, black pepper, and paprika until well combined. Pour the egg mixture evenly over the hashbrown mixture in the baking dish.
Sprinkle the shredded cheddar cheese on top of the casserole.
Bake in the preheated oven for 45-50 minutes, or until the eggs are set and the top is golden brown. Let it cool for about 10 minutes before slicing.