This easy hashbrown casserole is a simple and delicious dish perfect for breakfast or dinner. Packed with cheesy goodness and soft potatoes in every flavorful bite, this is a comforting dish the whole family will enjoy!
Preheat and prep. Preheat the oven to 350°F. Grease a 9×13 baking dish and set aside.
Mix casserole. In a large mixing bowl, combine the frozen hash browns, sour cream, diced onion, cream of mushroom soup, milk, half of the shredded cheese, and ham or bacon if using. Stir until evenly combined.
Assemble. Pour the mixture into the prepared baking dish and spread evenly. Sprinkle the remaining shredded cheese over the top.
Add butter. Slice the butter into about 12 even pieces and arrange them evenly over the cheese.
Bake covered. Cover the dish tightly with foil and bake for 60 minutes.
Uncover and finish. Remove the foil and bake for an additional 10 to 15 minutes, until hot and bubbly.
Rest and serve. Let the casserole rest for 5 to 10 minutes before serving to help it set.
Notes
Substitutions. Use cream of chicken soup instead of mushroom if preferred. Milk may be replaced with half-and-half or heavy cream. Sour cream can be swapped with plain Greek yogurt.
Make ahead. Assemble, cover, and refrigerate for up to 8 hours. Let sit at room temperature while the oven preheats, then bake as directed. Check for doneness 10 to 15 minutes early.
Storage. Store leftovers in an airtight container in the refrigerator for up to 5 days.