Preheat oven to 350 degrees.
Add the frozen potatoes (or hashbrowns), sausage, and cheese to a large bowl and mix together. Pour the mixture into a 9 x 13 baking dish that has been sprayed with cooking spray or coated with butter. I used mini casserole dishes in addition to the large pan.
In a large bowl, whisk the eggs with the milk, salt, and pepper
Pour the egg mixture over the hash brown mixture and pat down.
Bake for one hour.
*the middle should be firm and the edges golden brown when done