Sausage, Egg & Spinach Breakfast Casserole – Hearty, Simple, and Make-Ahead Friendly

This is the kind of breakfast that makes a morning feel easy. A warm, savory casserole loaded with sausage, fluffy eggs, tender spinach, and melty cheese—what’s not to love? It’s simple enough for a weekday and special enough for guests.

You can assemble it the night before or bake it right away. Either way, it’s hearty, comforting, and reliably delicious.

Why This Recipe Works

This casserole balances protein, veggies, and just the right amount of richness. The sausage brings bold flavor, while the spinach adds freshness and color.

Bread cubes or potatoes soak up the eggs, creating a satisfying, cohesive bite. A quick sauté step removes excess moisture, so the casserole bakes up set, not soggy. It’s also flexible: you can swap ingredients based on what you have and still get great results.

Ingredients

• 1 pound (450 g) breakfast sausage (pork or turkey; spicy or mild)
• 1 tablespoon olive oil (if needed, for sautéing)
• 1 medium yellow onion, diced
• 2 cloves garlic, minced
• 5–6 cups fresh baby spinach (about 5 ounces), roughly chopped
• 8 large eggs
• 1 1/2 cups milk (whole or 2%; or use half-and-half for richer texture)
• 1 teaspoon kosher salt, plus more to taste
• 1/2 teaspoon black pepper
• 1/2 teaspoon smoked paprika (optional, but great for depth)
• 1/2 teaspoon dried oregano or Italian seasoning
• 2 cups shredded cheese (cheddar, mozzarella, Monterey Jack, or a mix)
• 4 cups cubed day-old bread (French, sourdough, or brioche; 1-inch cubes) or 3 cups thawed hash browns
• Butter or cooking spray for greasing the baking dish

Step-by-Step Instructions

1. Prep the pan and oven. Heat the oven to 350°F (175°C).

   Grease a 9×13-inch baking dish with butter or cooking spray.

2. Cook the sausage. Set a large skillet over medium heat. Add the sausage and cook, breaking it up with a spoon, until browned and cooked through. If there’s excess fat, drain it.

   If the pan looks dry, add the olive oil before the next step.

3. Sauté the aromatics. Add the diced onion and cook until translucent, about 3–4 minutes. Stir in the garlic and cook for 30 seconds, just until fragrant.
4. Wilt the spinach. Add the chopped spinach to the skillet. Cook, stirring, until wilted and most of the moisture has evaporated.

   Season lightly with a pinch of salt and pepper. Remove from heat and let cool slightly.

5. Whisk the custard. In a large bowl, whisk the eggs, milk, 1 teaspoon salt, pepper, smoked paprika, and oregano until smooth. Stir in 1 1/2 cups of the shredded cheese, reserving 1/2 cup for the top.
6. Assemble the base. Spread the bread cubes (or hash browns) evenly in the prepared baking dish.

   Scatter the sausage-spinach mixture over the top.

7. Combine and pour. Pour the egg mixture evenly over the dish, pressing gently with a spatula so the bread absorbs the custard. Sprinkle the remaining 1/2 cup cheese over the top.
8. Rest or bake. For best texture, let the casserole sit for 10–15 minutes to absorb, or cover and refrigerate overnight. If baking right away, proceed to the next step.
9. Bake. Place the casserole in the oven and bake for 35–45 minutes, until the center is set and the top is golden.

   A knife inserted in the middle should come out mostly clean, and the center should no longer jiggle.

10. Finish and serve. Let it rest for 10 minutes before slicing. Garnish with fresh herbs (chives, parsley) if you like. Serve warm with hot sauce, salsa, or a simple side of fruit.

Storage Instructions

• Refrigerate: Cool completely.

  Cover tightly or transfer slices to airtight containers. Store for 3–4 days.

• Freeze: Wrap individual portions in plastic and foil, or use freezer-safe containers. Freeze for up to 2 months.

  Thaw overnight in the fridge.

• Reheat: Microwave slices for 60–90 seconds, or warm in a 300°F (150°C) oven for 10–15 minutes until heated through.
• Make ahead: Assemble up to 24 hours in advance. Cover and refrigerate, then bake straight from the fridge, adding 5–10 minutes to the bake time.

Benefits of This Recipe

• High in protein: Sausage and eggs keep you full and energized.
• Veggie-forward: Spinach adds nutrients without overpowering the dish.
• Flexible: Works with bread or potatoes, different cheeses, and various sausages.
• Great for crowds: One pan serves 8–10, and portions cleanly.
• Perfect for meal prep: Reheats well and freezes nicely.

Pitfalls to Watch Out For

• Soggy texture: If using bread, choose day-old or lightly toast fresh bread to prevent mushiness. Cook spinach until most moisture is gone.
• Undercooked center: If the top browns too fast while the middle is still jiggly, tent loosely with foil and continue baking until set.
• Over-salting: Sausage and cheese are salty.

  Season the egg mixture conservatively and taste the sausage mixture before adding more.

• Rubbery eggs: Overbaking can make the eggs tough. Pull the casserole as soon as the center sets.
• Greasy finish: Drain excess sausage fat to keep the casserole light and balanced.