Preheat your oven to 375F and grease a baking pan
In a skillet, brown your sausage and add your onions, cook until sausage is no longer pink and drain. Set aside.
Put your hashbrowns in the baking pan in a single layer.
Add your sausage on top of your hashbrowns.
In a bowl, combine your eggs and 1/2 a cup of cheese. mix up and add salt and pepper, pour your mix on top of the sausage.
Top your casserole with the remaining cheese. If you are making this the night before, cover your casserole with foil and put in the fridge, pull it out about 15 minuets before you plan on cooking it.
Bake your casserole covered for 30 minuets at 375, pull it out and take the foil off and bake an additional 10 mins or until cheese is bubbly. Let cool and serve!