Spinach and Mushroom Breakfast Casserole: A Savory Bread Pudding Recipe

When it comes to breakfast or brunch, I’m all about recipes that feel comforting, hearty, and a little indulgent—but still pack a nutritious punch. This Spinach and Mushroom Breakfast Casserole, a savory bread pudding recipe, checks all those boxes. It’s loaded with tender veggies, a touch of Swiss cheese, and fluffy, custardy bread that makes every bite irresistible.

The best part? You can prepare it ahead of time, making it a stress-free option for lazy weekends, holiday gatherings, or meal prep for the week ahead. Trust me, once you try this dish, it’ll earn a permanent spot in your recipe rotation!

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Why You’ll Love This Recipe

1. Make-Ahead Convenience: Prep it the night before, let it soak up all the flavors in the fridge, and bake it fresh in the morning.
2. Hearty and Healthy: Packed with protein from eggs and a generous serving of spinach, it’s as nutritious as it is delicious.
3. Customizable: Don’t have Swiss cheese? Swap it for cheddar or Gruyère. Prefer a different veggie? Bell peppers or zucchini would work beautifully.

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Ingredients

Custard:

• 5 large eggs
• 4 large egg whites
• 3 cups milk
• ¼ cup Dijon mustard
• Salt and pepper to taste

Bread Layer:

• 1 (16 oz) loaf of day-old French bread, cut into 1-inch slices

Veggie Mixture:

• ½ lb mushrooms, sliced
• 1 tsp minced garlic
• 1 large onion, chopped
• 2 (10 oz) boxes frozen chopped spinach, thawed and squeezed dry
• 1 tbsp flour
• Salt and pepper to taste

Topping:

• 1½ cups shredded Swiss cheese, divided

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Instructions

1. Prepare the Custard
   In a large mixing bowl, whisk together the eggs, egg whites, milk, Dijon mustard, salt, and pepper. Set aside.
2. Layer the Bread
   Coat a 13x9x2-inch baking dish with nonstick cooking spray. Arrange half of the bread slices in the dish to create an even layer.
3. Sauté the Veggies Heat a skillet over medium heat and coat it with nonstick cooking spray. Sauté the mushrooms, garlic, and onion until they’re tender and aromatic. Add the thawed and squeezed spinach, then sprinkle in the flour. Stir to combine and cook for an additional 2 minutes. Season the mixture with salt and pepper to taste.
4. Assemble the Dish
   Spread the sautéed veggie mixture evenly over the bread layer in the baking dish. Sprinkle 1 cup of the shredded Swiss cheese over the veggies. Top with the remaining bread slices.
5. Add the Custard
   Pour the prepared egg mixture evenly over the casserole, ensuring all the bread is soaked. Gently press the bread down with a spatula to help it absorb the liquid. Cover the dish with plastic wrap and refrigerate for at least 2 hours, or overnight for the best flavor.
6. Bake
   Preheat your oven to 350°F (175°C). Remove the casserole from the refrigerator and let it sit at room temperature while the oven heats. Sprinkle the remaining ½ cup of Swiss cheese over the top. Bake uncovered for 40–50 minutes, or until the casserole is puffed and golden brown.
7. Serve and Enjoy
   Let the casserole cool for 5–10 minutes before slicing and serving. Pair it with a fresh fruit salad or a side of crispy bacon for the ultimate brunch spread!

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Pro Tips

Bread Options: If you don’t have French bread, ciabatta or sourdough also work wonderfully.

Vegetarian-Friendly: This recipe is already vegetarian, but you can enhance the flavor with a dash of nutmeg or smoked paprika for extra depth.

Leftovers: Store leftovers in an airtight container in the fridge for up to 3 days. Reheat individual servings in the microwave or oven.

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This Spinach and Mushroom Breakfast Casserole is the ultimate combination of flavor, texture, and ease. Whether you’re hosting a brunch or simply treating yourself to a special breakfast, this dish is guaranteed to impress. Let me know how it turns out in the comments below—I’d love to hear your variations and serving ideas!