This cheesy baked Spinach Mushroom Casserole is naturally gluten-free, hearty, and comforting. Similar to a crustless quiche, it works wonderfully as a side dish, main course, or even breakfast. Its versatility and crowd-pleasing flavors make it a perfect addition to any meal.
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This recipe feeds a crowd, making it the perfect spinach casserole for holidays or entertaining. If you don’t have a crowd to feed, the leftovers always come in handy. We love making a big pan so we can reheat it all week for easy breakfasts. Talk about a morning lifesaver!
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Packed with protein and loaded with flavor, this casserole comes together quickly and makes for the perfect brunch recipe or side dish for dinner.
Enjoy it as written or use one of the flavor swaps below to make it into something new each time you whip it up. It’s a comforting blend of flavors that everyone will want more of.
Do you love egg casseroles as much as I do? They make easy work of breakfast or brunch! You might want to try the Baked Spinach, Cheese, and Egg Casserole, Baked Eggs With Asparagus, or the Egg Souffle Roll With Spinach, Mushroom, And Cheese.
Why You Will Love This Recipe
- Healthy: Naturally gluten-free this spinach mushroom casserole is packed with protein and vegetables too!
- Versatile: An egg casserole can be adapted easily and used for breakfast or dinner. This recipe is on repeat.
- Easy: Made with kitchen staples and prepped in just 15 minutes, this recipe is easy to whip up.
- Meal prep: This casserole can be made and frozen for when you need it making busy mornings a little less stressful or busy weeknights super easy.
Ingredients
See the recipe card for quantities.
Additions and Substitutions
Additions
- Protein: Add in crumbled, cooked bacon, chopped breakfast sausages, or cooked chicken to boost the protein of the casserole.
- Herbs and seasonings: Add in chopped jalapenos, fresh parsley, crushed red pepper, or more spices to create the flavors you’re craving.
Substitutions
- Cheese: Any cheese will work to create a savory flavor. Swap the cheddar cheese for feta or a combination of mozzarella and parmesan.
- Vegetables: In place of fresh mushrooms, you can use bell peppers or even finely chopped broccoli.
If you love the idea of an easy vegetable casserole but want something with broccoli, check out this broccoli casserole that is also super easy and delicious.
How To Make A Spinach Mushroom Casserole: Step-By-Step
Step 1: In a large skillet, sauté the onions in butter over medium heat until slightly cooked. Add in the fresh mushrooms. Cook the mushrooms until they start to brown. Set aside.
Step 2: Cook the frozen spinach in the microwave. Squeeze out the excess water and set aside.
Step 3: In a large bowl, add the spinach, cheese, egg, mushroom mixture, and spices. Mix well until everything is combined.
Step 4: Pour the spinach mixture into a greased casserole dish. Top the casserole with some extra cheese and bake it until the top is lightly browned about 35 minutes.
Let cool for 5 minutes before serving.
Pro Tip
Make sure to grease the dish or the outsides of your casserole will stick.
Storing the casserole
- Store - Once cooled, you can store the casserole in the refrigerator in an airtight container for 4 days.
- Freeze - You can also freeze the casserole as a whole or in individual slices. Let it cool and store it in a freezer-safe container or bag. If freezing in slices, separate them by layers of parchment paper. To enjoy it, let it thaw in the fridge overnight before reheating.
- Reheat - To reheat, place the casserole into the microwave or bake it again in the oven on low heat until warmed through.
Equipment
Use a 9x13 casserole dish for this recipe.
Yes! Make the egg bake and pour it into a greased dish. Then, wrap the dish in plastic wrap and store it in the refrigerator for 12-24 hours. When you need it, let it come to room temperature before baking it until cooked through.
Anything you want! This casserole is a meal all on its own so you can serve it by itself or with something simple like fruit. Or make it part of a bigger brunch and serve it with French toast, pancakes, or croissants.
Other Side Dish Recipes
Did you try this recipe? I would love to hear about it! Scroll down to the comment section and leave a ⭐️ rating and review. Share it on Facebook, Instagram, or Pinterest!
xoxoxo
Gwen
Spinach Mushroom Casserole
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Equipment
Ingredients
Instructions
- Preheat the oven to 375 degrees.
- Grease a 9x13 casserole dish and set aside.
- In a large skillet, saute the onions in butter over medium heat until soft and translucent.
- Add the mushrooms. Saute until the mushrooms are just starting to brown. Season with a touch of salt. Turn off the heat and set aside.
- Cook the spinach in the microwave according to the package. Drain the water out of the cooked spinach by squeezing the spinach in a colander over the sink.
- Place the spinach into a bowl.
- Add the onions and mushrooms to the bowl.
- Add the rest of the ingredients and combine.
- Pour the mixture into the greased casserole dish. Add more cheese if desired.
- Bake for 35 minutes to an hour. The top should look lightly brown and the cheese should be melted.
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