- Preheat oven to 350 degrees F (175 degrees C). Grease a 9×13-inch baking dish.
- Arrange hash brown patties on the prepared baking dish. Sprinkle Cheddar cheese and ham over patties.
- Beat eggs, milk, salt, and mustard in a large bowl using a whisk; pour over ham. Cover baking dish with aluminum foil.
- Bake in the preheated oven for 1 hour. Remove foil and bake until edges are golden brown and a knife inserted in the center comes out clean, about 15 minutes more.