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egg casserole with croutons, sausage and mushrooms.

Breakfast Egg Casserole with Croutons, Sausage, Mushrooms and Spinach

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Start off your day delicious with my egg casserole with croutons recipe. The hearty dish with breakfast sausage, mushrooms, spinach, cheddar cheese and toasted croutons is the perfect dish for breakfast or brunch. It's my go-to recipe and a huge hit whenever I serve it.


Units Scale
  • 3 tablespoons salted butter, divided
  • 16 ounces breakfast sausage
  • 8 ounces mushrooms, sliced
  • 8 ounce bag of baby spinach
  • 12 large eggs
  • 1/2 cup whole milk
  • 1 teaspoon Dijon mustard
  • 1 1/2 teaspoons kosher salt, divided
  • 1 teaspoon fresh ground black pepper, divided
  • 2 cups shredded sharp cheddar cheese, divided
  • 4 cups fresh bread cubes
  • olive oil
  • 2 tablespoons chopped fresh parsley


  1. Prep the baking dish: Preheat the oven to 375 degrees F. Grease a 9 x 13 inch baking dish with about 1 tablespoon of the butter. Set aside.
  2. Cook the sausage: In a large sauté pan over medium heat, add the breakfast sausage. Sauté the sausage and break it into small pieces as it cooks. Cook for 8-10 minutes or until it is browned and crispy in spots and cooked through. Remove the sausage from the pan to a bowl and set aside.
  3. Sauté the vegetables: In the same sauté pan over medium heat, add the remaining 2 tablespoons of butter. When the butter has melted, add the sliced mushrooms. Stir and sauté until the mushrooms lose most of their water and are golden brown, about 5-6 minutes. Add the spinach. Stir and cook until the spinach is wilted, about 3-4 minutes. Remove the pan from the heat.
  4. Make the egg mixture: In a large bowl crack the eggs. Whisk to eggs to combine the yolks and the whites. Stir in the whole milk, Dijon mustard, 1 teaspoon of kosher salt and 1/2 teaspoon of black pepper.
  5. Add the mix-ins: Add the cooked sausage, mushrooms, spinach and 1 1/2 cups of the shredded cheese. Stir to combine the ingredients.
  6. Add to baking dish: Pour the egg mixture into the prepared baking dish. Set aside.
  7. Season the bread cubes: Place the bread cubes in a large bowl. Drizzle with about 1-2 tablespoons of olive oil. Season with the remaining 1/2 teaspoon each of kosher salt and black pepper. Toss to coat the bread cubes with the seasonings.
  8. Add the bread cubes: Distribute the seasoned bread cubes over the egg mixture. Press down lightly. Sprinkle the remaining 1/2 cup of shredded cheese over the cubes.
  9. Bake the casserole: Bake the casserole for 35-40 minutes. The center should be set. The internal temperature of the casserole should be 160 degrees F on a digital thermometer.
  10. Serve: Remove the casserole from the oven. Sprinkle with the chopped parsley. Let cool 5 minutes. Cut into squares and serve.


Make ahead and refrigerate ~ Completely cool the baked casserole. Cover the baking dish with plastic wrap and store in the refrigerator up to 4 days. Or cut the casserole into individual pieces and store in airtight containers. These meal prep containers are my favorite.

Make ahead and freeze ~ Completely cool the baked casserole. Cover the baking dish with plastic wrap and then foil. Store in the freezer up to 1 month. Or cut the casserole into individual pieces and store in airtight containers.

Make to bake later ~ Prepare the casserole to the step of filling the baking dish with the egg mixture. Cover with plastic wrap and store in the refrigerator overnight or up to 24 hours. The next morning, toss the bread cubes with the olive oil and seasonings. Remove the casserole from the fridge. Top with the seasoned bread cubes and the 1/2 cup of shredded cheese. Bake at 375 degrees F. You may need to add 10-20 minutes to the baking time to account for the cold dish and egg mixture.

Reheating directions ~ Place individual pieces of the casserole on a microwave safe plate and cover loosely with plastic wrap. Microwave on 60 percent power at 30 second intervals until heated through. To reheat the whole casserole, cover the dish with foil. Heat in a 350 degree F oven for about 30 minutes. Remove the foil the last 5-10 minutes of heating to crisp up the croutons.

Nutritional information is an estimate and based on the ingredients and cooking methods used in this recipe.

  • Prep Time: 20 minutes
  • Cook Time: 40 minutes
  • Category: entrée
  • Method: cook on stove top and bake in oven
  • Cuisine: American


  • Serving Size: 1/12 of casserole
  • Calories: 375
  • Sugar: 1.9 g
  • Sodium: 908 mg
  • Fat: 23.6 g
  • Saturated Fat: 9.4 g
  • Unsaturated Fat: 0 g
  • Trans Fat: 0 g
  • Carbohydrates: 9.7 g
  • Fiber: 1.7 g
  • Protein: 32.1 g
  • Cholesterol: 292 mg