Old Fashioned Breakfast Casserole

If you want a comforting, nostalgia-filled breakfast that’s easy to prepare and packed with flavor, this Old Fashioned Breakfast Casserole is a must-try. It’s a classic dish that shows up at potlucks, family gatherings, and holiday mornings. The combination of hashbrowns, sausage, sautéed vegetables, eggs, and sharp cheddar creates a hearty, crowd-pleasing bake you can assemble ahead of time and bake when you’re ready to serve.

This casserole is especially nice during the holidays or whenever you’re feeding a group. It can be put together the night before, refrigerated, and baked the next morning—freeing you up to enjoy guests instead of fussing over the stove. It also reheats very well, so it’s ideal for leftovers and busy weekday breakfasts.

Ingredients

• Avocado oil cooking spray
• 3 cups frozen diced hash brown potatoes
• 1 teaspoon garlic powder
• ½ teaspoon smoked paprika
• 1 teaspoon marjoram (or dried thyme)
• 1 pound bulk breakfast sausage
• ¾ cup small-diced red bell pepper
• ½ cup finely diced yellow onion
• 4 cups packed baby spinach
• 12 large eggs
• ½ cup milk
• 1½ teaspoons kosher salt
• ½ teaspoon black pepper
• ½ teaspoon garlic powder (additional)
• 1 cup shredded sharp cheddar cheese

Step-by-step Instructions

Step 1: Prep the casserole dish

Preheat your oven when you’re ready to bake (see baking step). Spray a 9×13-inch baking dish thoroughly with avocado oil cooking spray to prevent sticking.

Step 2: Add the potato layer

In a bowl, combine the frozen diced hash browns with 1 teaspoon garlic powder, ½ teaspoon smoked paprika, and 1 teaspoon marjoram (or dried thyme). Toss until the spices are evenly distributed, then spread the seasoned hashbrowns in an even layer in the bottom of the prepared baking dish. Set aside.

Step 3: Cook the sausage

Heat a large skillet over medium-high heat and spray lightly with avocado oil. Add the bulk breakfast sausage and cook, breaking it into small pieces, until fully browned and no longer pink, about 6–8 minutes. Drain off excess fat and spread the cooked sausage in an even layer over the hashbrowns.

Step 4: Cook the vegetables

Reduce the skillet heat to medium and spray again with avocado oil. Add the diced red bell pepper and diced yellow onion with a pinch of salt and pepper. Sauté until the vegetables are tender, about 4 minutes. Add the packed baby spinach and cook, stirring, until wilted, about 2–3 more minutes. Spread the sautéed vegetables over the sausage layer in the casserole dish.

Step 5: Finish assembling the casserole

In a large bowl, whisk together 12 large eggs, ½ cup milk, 1½ teaspoons kosher salt, ½ teaspoon black pepper, ½ teaspoon garlic powder, and 1 cup shredded sharp cheddar cheese until well combined and slightly frothy. Pour the egg mixture evenly over the layered potatoes, sausage, and vegetables.

Step 6: Chill (optional)

Cover the dish with plastic wrap and refrigerate for at least 30 minutes or up to 24 hours. Chilling helps the casserole set and makes it convenient to prepare ahead when entertaining.

Step 7: Bake the casserole

When you’re ready to bake, preheat the oven to 350°F (175°C). Place the uncovered casserole in the oven and bake until the eggs are fully set and the top is lightly golden, about 40–45 minutes. A knife inserted into the center should come out clean.

Step 8: Rest and serve

Remove the casserole from the oven and let it rest for about 5 minutes before slicing. Serve warm in squares. This casserole pairs well with fresh fruit, toast, or coffee for a complete breakfast spread.

Recipe Notes & Tips

• Make-ahead: Assemble the casserole the night before, cover, and refrigerate. Bake the next morning from chilled—just add a few extra minutes to baking time if still quite cold.
• Substitutions: Swap the breakfast sausage for cooked bacon, ham, or a plant-based sausage if you prefer. Use different cheeses like Monterey Jack, Colby, or a blend for varied flavor.
• Vegetable variations: Replace or add vegetables based on what you have—mushrooms, zucchini, or broccoli (pre-cooked) can all work. Adjust sauté time as needed to remove excess moisture.
• Leftovers: Store cooled leftovers covered in the refrigerator for up to 3–4 days. Reheat individual portions in the microwave or warm the whole dish in a 325°F oven until heated through.

Frequently Asked Questions

Nutrition (per serving, approximate)

• Calories: 272 kcal
• Carbohydrates: 13 g
• Protein: 16 g
• Fat: 18 g
• Sodium: 670 mg
• Fiber: 2 g

Nutrition information is an estimate and should be used as a guideline.

Additional Info

Servings: 12. Author: Alex Snodgrass. If you try this recipe, leave a comment to share how it turned out and any swaps you made—it’s always great to hear new variations and tips from readers.

Food Photography and Styling by Eat Love Eats.