Cheesy Mushroom Spinach Egg Casserole
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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 3 months in the freezer.
Ingredients for spinach and mushroom casserole
- unsalted butter divided
- medium onion chopped (about 7 ounces)
- sliced mushrooms
- baby spinach
- 2 cloves garlic minced
- eggs
- Cottage Cheese
- sharp cheddar cheese shredded
- kosher salt
- black pepper
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.
In a separate bowl, whisk together the eggs, cheeses, green onions, and spices.
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?
Spaghetti Squash with Tomatoes and Mushrooms
Spinach and Mushroom Breakfast Casserole
Ingredients
- 5 Tablespoons unsalted butter divided
- 1 medium onion chopped (about 7 ounces)
- 8 ounces mushrooms sliced
- 12 ounce baby spinach
- 2 cloves garlic minced
- 6 eggs beaten
- 16 oz. cottage cheese
- 12 ounces sharp cheddar cheese shredded
- 3 green onions sliced
- 1 teaspoon kosher salt
- 1/2 teaspoon black pepper
Instructions
- 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.
Sounds delicious! I love it, so I’m definitely going to give this stew a try. Thanks for sharing the recipe!
This was SO good! I cut the recipe in half, but I wish I would have made the whole thing and froze the leftovers for a quick breakfast. I thought cottage cheese seemed like a weird ingredient, but it works and you can’t tell it’s there.
just extra protein! Yep, I usually freeze it in sections and have a few for quick breakfasts!
I have been making this for Years for Xmas morning! Sometimes I switch it up by adding g a great chicken sausage! But this made for a quick delicious Xmas morning breakfast with minimal clean up. This is so good. Leftover are even better!
This sounds yummy! I would love to try it!
I love this recipe and though you have it under breakfast, it’s also great for brunch or dinner. I also use this as a meal prep for weeks I need a premade meal in the fridge.
Giveaway
What is the serving size in all of these recipes ?
What do you mean? The recipe makes 12 servings. The nutritional information is listed for one serving.
She means what is the exact serving size 1/2 cup, a 4×4 square or use your 13×9 tray and cut into 12 pieces?
Its not so simple for some
I guess I’m confused? The instructions call for a 13 x 9 baking dish. Then cut it into 12 equal servings. Of course the portions won’t be exact,, but close.
I love the cheesy mushroom casserole. It is now my go to for breakfast or brunch especially when we have company. Absolute best
Tea cup
Love this recipe – the perfect balance of flavors. I make huge batches of this and then divide and put the uncooked mixture in the freezer. Quart size bag makes a perfect 8×8 pan. Need a 9×13 thaw 2 bags or save in gallon bags
love that you’ve figured this out! thanks!
This is very good, but a little too salty for my taste. I will try cutting the salt in half the next time.
thanks for your feedback. Everyone has different tastebuds, I’m glad you enjoyed the flavor. I wonder if the cheese you used was saltier than mine?
I added a cup of chopped sautéed red bell pepper for color, and some dried thyme, rosemary and a dash of ground nutmeg.
Can you make this ahead? I have a baby shower on Saturday….would like to make it Friday and cook saturday morning??? What’s best?
absolutely! I assemble it the night before and cover it in foil. Pull it out when you preheat the stove to warm up a bit.
I made this delicious dish, and it tasted just like a crustless quiche, only better! I only made a few adjustments for my personal taste: I didn’t have unsalted butter, so I used salted and omitted the addition of extra salt; I triple-dosed on the freshly ground black pepper; I used a blend of mozzarella and medium cheddar cheese; I whipped the cottage cheese until light and creamy before blending; and I added grape tomato halves and parsley on the top for some extra colour. Well, I could even eat this cold – it’s just like healthy pizza! Thank you so much for sharing. I absolutely adore it – and I love that it can be varied based on what you have on hand. xo
Oh thank you so much for leaving such a nice review!
Forgot to leave a five-star rating, so here it is!
awww! Thank you!
what a great recipe. been looking for one to gain my protein intake. this is great. 2 of the 12 pcs for lunch is just about right. Also like the idea of adding red pepper and/or sausage meat as other commented. Will definitely give that a try next time.
Thanks for sharing!
thanks so much Polly! It is a delicious way to get in extra protein!
I made this breakfast dish for the first time at a women’s gathering and everyone LOVED it! I added 1 small can of mild diced green chiles and about a 1/2 cup of sliced ham bits. It’s a keeper/2 thumbs up!
I made this breakfast dish for the first time at a women’s gathering and everyone LOVED it! I added 1 small can of mild diced green chiles and about a 1/2 cup of sliced ham bits. It’s a keeper/2 thumbs up!
Sounds delish! Thank you!
Big fan of this recipe! First made it about a year ago to serve at a baby shower for a gluten-free friend. Now it’s become a staple in my home!
oh nice! Thank you. It’s my go-to when we have a brunch.
Great!!!
When baking later, do you leave the foil on or take it off? Looking forward to making it for Easter brunch this year.
I leave the foil on.
This breakfast casserole is the bomb. I made it as is the first time and second time I added breakfast sausage (hot) and it was delicious both ways. I urge you trying this, you won’t be disappointed. It makes for an easy breakfast for several days. I serve with fresh fruit.
thank you so much Linda!
Making this for Easter brunch. Six eggs doesn’t sound like enough for a 9 x 13 pan. Is that a typo?
Yes, it should turn out exactly like the photos I took. You can certainly add more eggs if you like and it will be more eggy and puffier!