Prepare a 9"x13" casserole by spraying it with cooking oil spray. In a large bowl, mix together hash brown potatoes, eggs, 1/2 of the cheese, ham, sour cream, onions, milk, melted butter, and seasonings.
Pour hash brown casserole ingredients into the prepared casserole dish and top with remaining shredded cheese.
Bake for 45-50 minutes, or until hot and bubbly and golden on top, and the edges of the breakfast casserole are puffy.
Notes
Make ahead directions: Prepare casserole as directed in steps 2 and 3, then cover with plastic wrap or foil, and refrigerate for up to 3 days. Then follow baking directions, baking for 50 minutes.Leftovers will keep well for up to 4 or 5 days in the refrigerator. Let the casserole cool completely and transfer to a sealed container before placing in the fridge.If you plan to make ahead this breakfast casserole and freeze it, I suggest you use a foil container: Not only is it freezer-safe, but the container can be safely used in the oven as well to reheat it.To make ahead and freeze this hash brown breakfast casserole: Follow steps 2 and 3, using a freezer-safe container (I recommend using a foil container). Cover with a layer of aluminum foil, and freeze for up to 3 months. Then bake from frozen (do not defrost) as directed, adding an extra 15 minutes of baking time or so until it's heated throughout and the cheese is golden.