Cook sausages if needed, and cut into 1-inch pieces.
Grease a 9x13-inch baking dish with pan spray. Spread frozen hashbrowns in the bottom of the dish. Season heavily with salt and pepper.
Top the hashbrowns with cut up sausage links and 1 cup of shredded cheddar cheese.
Whisk eggs with milk, season with salt and pepper. Pour the egg mixture over the whole casserole. Sprinkle with most of the green onions and remaining ½ cup shredded cheddar cheese.
Bake at 350 degrees Fahrenheit for 50-60 minutes or until eggs are baked through covering the casserole with foil the last 20 minutes. Test doneness in the center of the casserole when the pan is jiggled or a knife is inserted. Sprinkle with extra green onions. Enjoy with ketchup or salsa.