Cheesy mushroom spinach egg casserole is easy to make, great for a gluten-free breakfast casserole, and it’s meatless!
This spinach mushroom casserole has been making an appearance at our house for breakfast and brunch for nearly 30 years.
At first, it started out as a “strata” which had chunks of white bread.
After we started cutting back on gluten and bread in general, I figured out a way to omit it from this mushroom casserole recipe without affecting the taste. (This post was originally published on December 29th, 2011. As an Amazon Affiliate, I earn commission on qualifying purchases.)
The result, little did I know at the time, was a low-carb, spinach breakfast casserole. I now make this dish whenever we have guests staying over.
What’s in a Breakfast Casserole?
Every good breakfast casserole starts with a base of eggs. But from there you can add just about anything!
This egg spinach mushroom casserole version is vegetarian, but you can also add diced ham or sausage.
I make another casserole with just Hatch chiles, that mimics Chile Rellenos (but without the carbs), for those who like it spicy!
For the cheese, you can go crazy! Sharp cheddar is the perfect foil for casseroles with spinach, eggs, and mushrooms.
Asparagus Mushroom Crustless Quiche looks a little fancier if you are having just a few people over. It’s delicious for lunch as well. If you don’t have a sensitivity to gluten, you can try this Coronation quiche with spinach and leeks.
Can I Make a Gluten-Free Breakfast Casserole Ahead of Time?
There are two ways you can make this casserole ahead of time.
First, you can prep the entire egg spinach casserole, cover it, and refrigerate it until the morning.
The other way is you can make and refrigerate it and then simply reheat it the next morning.
To re-heat, turn the oven to 325 degrees F. Put the covered casserole into the oven and heat until hot and bubbly, about 35 minutes.
If you’re doing meal prep and you’d rather have smaller portions, you can refer to this recipe for gluten-free egg “muffins”.
It’s a great way to make this spinach and mushroom recipe in muffin cups! I love this silicone muffin pan!
It gives adjusted cooking time and ingredient amounts. Feel free to use whatever vegetables and cheese you like.
Can You Freeze Breakfast Casseroles?
Yes! Just cut into individual portions and wrap well.
This is a great way to have a grab-and-go breakfast! Just defrost the night before in the refrigerator and heat until warm and bubbly in the microwave.
This spinach egg casserole will last about 6 months in the freezer.
How to Make Spinach, Egg, and Mushroom Casserole
Preheat the oven to 350* F. Use butter to grease a baking dish.
Heat 4 Tablespoons of butter in a large skillet and sauté onions and mushrooms, then add garlic.
After another minute or two, add spinach, and let it wilt.
Drain excess water from the spinach mixture and chop finely.
Add spinach and mushrooms to the egg mixture and mix well.
Pour into a baking dish and smooth. If planning on refrigerating to bake later, wrap well in foil. It is now ready to bake.
Bake for 45-50 minutes or until the top is golden brown and the center is done.
Add an additional 5-10 minutes to cooking time if baking from the refrigerator, and enjoy!
Looking for more vegetarian dishes?
Spinach and Mushroom Breakfast Casserole
- Pre-heat oven to 350* F. Use 1 Tablespoon butter to grease 13″ X 9″ baking dish.
- Heat 4 Tablespoons butter in a large skillet or sauté pan, and sauté yellow onions and mushrooms, about 3-4 of minutes until onions are translucent and mushrooms are soft. Add garlic and sauté another minute.
- Add spinach, a handful at a time, and sauté. Cover skillet and let spinach wilt, about 5 minutes.
- Let cool, drain excess liquid, and chop more finely.
- In a separate bowl, whisk eggs, cottage cheese, cheddar cheese, green onions, and salt and pepper. Add cooked spinach and mushroom mixture.
- Mix well and pour into baking dish.
- Bake for 45-50 minutes or until top is golden brown and center is done.