I heat the oven to 375°F and grease a 9-by-13-inch baking dish.

I cook the sausage and onion in a skillet until the sausage browns. I drain any extra grease.

I spread the hash browns in the dish, then add the sausage mixture and cheese.

I whisk the eggs, milk, salt, and pepper in a bowl. I pour this over everything.

I bake for 40 to 45 minutes, until the center sets and the top turns golden. I let it rest for 5 minutes before serving.