Sausage and Mushroom Breakfast Casserole with caramelized onion, spinach, and feta cheese is a winning healthy brunch recipe! Serve it up with your favorite side dishes for a complete meal and an amazing weekend breakfast or Sunday brunch.
If you’re into mushrooms, sausage, and eggs, this simple yet flavorful sausage and mushroom breakfast casserole is for you!
Ideal for special occasions but also great for general meal prep for weekday meals, this dish comes together quickly and is a great household staple! Perfect for the entire family for busy mornings.
Sausage egg breakfast casserole recipes should almost be their own category on The Roasted Root.
My Sweet Potato Sausage and Kale Breakfast Casserole, Greek Sausage Breakfast Casserole with Spinach, Mediterranean Breakfast Casserole, and Zucchini Herb Sausage Breakfast Casserole are just scratching the surface, and all of them have been reader favorites.
The fresh taste and filling characteristic of the egg casserole makes them ideal for sharing with friends and family for breakfast or brunch.
You can easily use this as an overnight breakfast casserole where you prep the casserole the night before and bake it off the next morning. A great recipe to add to your arsenal of make ahead recipes.
Let’s discuss the simple ingredients needed for this healthy casserole recipe!
Sausage and Mushroom Breakfast Casserole Ingredients:
Eggs: The main ingredient in any egg-based breakfast casserole, we need an even dozen eggs to make this tasty dish.
Avocado Oil: Used to sauté the onion, mushrooms, and garlic and cook the breakfast sausage, avocado oil is a great high-temperature cooking oil. Its neutral flavor and the fact that it tolerates high heat makes it ideal for sautéing or roasting. If you only have olive oil on hand, feel free to go with olive oil.
Yellow Onion: Sautéed yellow onion until it is deeply golden-brown or even caramelized adds a great deal of rich, robust flavor.
Mushrooms: Adding a great deal of mushrooms to an egg casserole generates lovely earthy flavor and a nice texture. We use 1 whole pound of mushrooms to ensure we’re getting plenty of flavor!
Garlic: Garlic lovers, here is a marvelous placement for the lovely clove! I use 8 cloves of garlic to be sure plenty of garlicky flavor shines through. Feel free to adjust the amount up or down depending on your personal taste.
Breakfast Sausage: The star of the show here! Use your favorite brand of breakfast sausage to add flavor, lots of protein, and plenty of substance to this healthy egg casserole recipe. I go with turkey sausage, which I pick up from Whole Foods, which is lower in fat than pork sausage but still has amazing flavor.
Baby Spinach: Adding an infusion of vitamins and minerals, incorporating baby spinach into a breakfast casserole like this is an easy way of getting a lot of greens since it cooks down so much. Feel free to replace the spinach with kale or chard.
Feta Cheese: That creamy burst of tangy flavor makes feta a brilliant addition to a breakfast casserole. If you want to swap it out for another cheese, such as goat cheese or grated cheddar cheese, mozzarella cheese, gouda or gruyere, feel free to do so! You can also add more cheese depending on how much you love it. You can incorporate all kinds of cheese!
Sea salt: Sea salt helps bring all of the flavors out into one cohesive whole! I sprinkle sea salt on the veggies while they are sautéing to draw out the water, and I also add it to the eggs when I whisk them to ensure everything is well-seasoned. Use the amount that is suitable for you.
Optional Additions: You can add fresh or dried herbs for more rustic flavor, some red pepper flakes for a little heat, or ½ cup of heavy cream or milk to make the eggs turn out more tender. Green onions, bell peppers, tater tots, are all great additions.
To make the casserole lower fat you can buy a carton of egg whites and substitute some of the whole eggs for egg whites.
Let’s bake this healthy breakfast casserole!
How to Make Sausage and Mushroom Breakfast Casserole:
Preheat the oven to 350 degrees F and lightly spray a large (13” x 9”) casserole dish or baking dish with cooking spray
Heat the avocado oil over medium-high heat in a large nonstick skillet. After allowing the skillet to warm up for a minute or two, add the onion and sauté it for about 8 minutes, until it is golden-brown.
Add the mushrooms and sea salt, stir well, and cover the skillet. Allow the mushrooms to cook, stirring occasionally, until they turn brown and much liquid has leached out, about 8 minutes.
Remove the lid and stir in the garlic, followed by the ground turkey.
Use a spatula to break up the ground turkey and continue cooking, stirring constantly, until the turkey is cooked through, about 5 to 8 minutes.
Add the baby spinach to the skillet, cover, and allow it to cook until the spinach has wilted, about 2 to 3 minutes.
Stir the turkey and mushroom mixture well, then transfer it to the casserole dish, spreading it into an even layer.
Sprinkle the feta cheese over everything.
Crack the eggs into a large bowl and beat them until very well combined.
Pour the egg mixture over the meat mixture evenly. If need be, you can stir everything around a bit to ensure the ingredients are evenly distributed.
Bake on the center rack of the preheated oven for 40 to 50 minutes, or until the casserole has set up in the center and has cooked through.
Allow the casserole to cool for 20 minutes before slicing into individual pieces and serving (this will allow for cleaner slices). Serve it with a dollop of sour cream or yogurt, hot sauce, crispy bacon, and chopped green onions for a lovely holiday breakfast.
If desired, serve the sausage breakfast casserole with side dishes such as green salad, fresh fruit salad, roasted vegetables, or hash browns.
I like this make ahead breakfast casserole with Sweet Potato Hash with Bacon and Spinach and my Vegan Blueberry Scones.
Store any leftover breakfast casserole in an airtight container in the refrigerator for up to 5 days. You can also cover the casserole dish with plastic wrap to save it in the refrigerator.
More Healthy Breakfast Recipes:
- Bacon and Egg Casserole
- Roasted Veggie and Avocado Breakfast Burritos
- Easy Spanish Omelette
- Pesto Chicken Omelette
- Spinach Frittata with Zucchini Sun-Dried Tomatoes and Goat Cheese
- Broccoli Cheddar Egg Hashbrown Casserole
Enjoy this hearty easy breakfast casserole recipe!
Sausage and Mushroom Breakfast Casserole
Ingredients
- 2 Tbsp avocado oil
- 1 medium-sized yellow onion
- 16 ounces mushrooms chopped
- ¾ tsp sea salt
- 8 cloves garlic minced
- 1 pound breakfast sausage*
- 5 ounces baby spinach
- 6 ounces feta cheese
- 12 large eggs
Instructions
- Preheat the oven to 350 degrees F and lightly spray a large (13” x 9”) casserole dish or baking dish with cooking spray.
- Heat the avocado oil over medium-high heat in a large nonstick skillet. After allowing the skillet to warm up for a minute or two, add the onion and sauté it for about 8 minutes, until it is golden-brown.
- Add the mushrooms and sea salt, stir well, and cover the skillet. Allow the mushrooms to cook, stirring occasionally, until they turn brown and much liquid has leached out, about 8 minutes.
- Remove the lid and stir in the garlic, followed by the ground breakfast sausage. Use a spatula to break up the ground turkey and continue cooking, stirring constantly, until the turkey is cooked through, about 5 to 8 minutes.
- Add the baby spinach to the skillet, cover, and allow it to cook until the spinach has wilted, about 2 to 3 minutes.
- Stir the turkey and mushroom mixture well, then transfer it to the casserole dish, spreading it into an even layer. Sprinkle the feta cheese over everything.
- Crack the eggs into a large bowl and beat them until very well combined.
- Pour the egg mixture over the meat mixture evenly. If need be, you can stir everything around a bit to ensure the ingredients are evenly distributed.
- Bake on the center rack of the preheated oven for 40 to 50 minutes, or until the casserole has set up in the center and has cooked through.
- Allow the casserole to cool for 20 minutes before slicing into individual pieces and serving (this will allow for cleaner slices). Serve it with a dollop of sour cream or yogurt, hot sauce, crispy bacon, and chopped green onions for a lovely holiday breakfast.
Notes
Nutrition
I also see eggs aren’t listed on the ingredients list on the recipe. But I do count 12 eggs in the bowl in the directions section – are 12 eggs correct? Thanks for your help. I enjoy your healthy recipes and your healing story. Many blessings to you.
My apologies! You’re correct – it’s 12 eggs! I added them to the recipe 🙂
You forgot to add the eggs in your ingredients.
LOL, how embarrassing! Thanks for catching that. It’s 12 eggs 🙂
Hi Julia
The eggs are not listed in the ingredients. I count 12 in the bowl. Is that right? Thanks, Love this site and use many of the recipes!! Great Work! Kim
So sorry about that! Yup, 12 eggs is correct! Thanks so much for the sweet compliment and let me know if you have any other questions! xoxo