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Delicious ultimate overnight breakfast casserole topped with fresh herbs.

The Ultimate Overnight Breakfast Casserole

A comforting and forgiving breakfast bake made with layers of frozen hash browns, browned sausage, and creamy egg custard, perfect for busy mornings.
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Prep Time 20 minutes
Cook Time 1 hour 10 minutes
Total Time 1 hour 30 minutes
Servings: 8 servings
Course: Breakfast, Brunch
Cuisine: American
Calories: 350
Ingredients Method Notes

Ingredients
  

Main Ingredients
  • 1 pound breakfast sausage (turkey, chicken, lean beef, or gluten-free plant-based sausage) Choose a brand labeled gluten-free
  • 30 oz frozen hash browns (shredded or diced, plain, not seasoned) Frozen works best for texture and convenience
  • 8 large eggs Room temperature helps even cooking
  • 1 cup milk (whole or 2%) Use dairy or a creamy unsweetened plant milk labeled gluten-free if needed
  • 1 cup sour cream Plain Greek yogurt can be used as a swap
  • 2 cups shredded cheddar cheese Sharp or mild, depending on taste
  • 1/2 teaspoon salt
  • 1/4 teaspoon black pepper
  • 1/4 cup chopped green onions Plus more for garnish
Optional Add-ons
  • 1 small diced bell pepper (red or orange) For sweetness
  • 1 cup sautéed mushrooms Cook until moisture is reduced
  • 1 cup fresh spinach Briefly wilted or chopped; squeeze out excess moisture
  • 1/2 cup diced tomatoes Fold in just before baking to avoid excess liquid
  • 1 teaspoon onion powder or garlic powder For an extra savory note
  • 1/2 teaspoon smoked paprika For warmth and color
  • 1 to 1 1/2 cups mixed shredded cheese (Monterey Jack, mozzarella, or blend) For melty stretch

Method
 

Preparation
  1. Heat a medium skillet over medium heat. Add the breakfast sausage and cook, breaking it into bite-sized pieces until nicely browned and cooked through (7–10 minutes). Drain any excess fat and set aside to cool slightly.
  2. In a large mixing bowl, whisk together the eggs, milk, and sour cream until smooth. Stir in salt, pepper, and any optional spices.
  3. Lightly grease a 9x13-inch baking dish with butter or oil.
  4. Spread half of the frozen hash browns in the prepared dish. Layer half of the cooked sausage, then half of the cheese. Repeat the layers.
  5. Pour the egg mixture evenly over the layers, gently pressing down with a spatula.
  6. Cover tightly with foil and refrigerate overnight (or up to 24 hours).
Baking
  1. Preheat the oven to 350°F (175°C). Remove casserole from the fridge and bake covered for 45 minutes.
  2. Remove the foil and bake for an additional 20–25 minutes until golden, bubbling, and set.
  3. Let the casserole rest for 10 minutes before slicing. Serve warm, garnished with chopped green onions.

Notes

Leftovers keep well in the fridge for 3–4 days. Can be reheated gently. Perfection isn’t required; small mistakes can often lead to delicious results.