Slow Cooker Breakfast Casserole - super simple overnight breakfast recipe that tastes great. Make the casserole before going to bed and breakfast is ready when you wake up. You can't beat that! Hash browns, sausage, cheese, eggs, milk, dry mustard, onion powder, garlic powder, salt, and pepper. This is a great recipe for overnight guests, holiday mornings, hectic weekday mornings, potlucks, or even dinner. Whip up some biscuits, grits, or fruit, and enjoy!