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 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.
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.
Awesome and so flavorful! I added two extra eggs and a 1/2 tsp of dried mustard because I do that for every breakfast casserole. Will definitely make this again!
Have been making this for years and love it. It’s my go-to breakfast dish for a crowd. I’ll add meat as the crowd desires or not and it’s fantastic. Thank you so much for this amazing timeless recipe!!
So glad you like it! It’s very versatile!
Everyone loved this casserole when I served to friends for brunch. I have made several breakfast casseroles but this one is my favorite now.
Thank you so much! It’s great for company.
I don’t have cottage cheese or ricotta, will it still be good, or is there another substitute?
You can try it, but it won’t be the same. The cottage cheese is part of what makes it lighter and fluffier.
I can’t count the number of times I have made this casserole. I make it at least twice a week for myself and my mom. I’m a type 2 diabetic and this is one of the dishes I can eat freely and my blood sugar isn’t affected at all. I’ve shared this recipe to friends and family and it is always a big hit. I never could remember where I first saw this recipe until I was determined to do a search. It ended here. This deserves more than a 5 star. I can make it with my eyes closed now.
I am so happy to hear! Thank you!
This is a go-to recipe that is quick, easy and uses ingredients I always have on hand. A bonus: it’s delicious.
Oh, I am so glad you like it!
I’m a type two as well! Anything I can cook and eat and not worry about my BS! I love spinach and mushrooms! Thank You!
oh I’m so glad! Thanks!
I’m not clear if I should cover the top with foil before baking it. The recipe says that it will be golden brown, but would it be golden brown with foil on top? It’s not clear. Thank you!
no need to cover it!
This is the best egg bake recipe I have ever tried. When we make it for guests, they often say the same thing, “This is the best egg bake I have ever had!” We make it for dinner sometimes, too, and change up the recipe. For example, adding ham or bacon or broccoli are very tasty.
So nice to hear! Thank you!
Very tasty! Quick and easy to make.
glad you enjoyed it!
Made this and absolutely LOVE!!! Added red pepper flakes otherwise wouldn’t change a thing
Red pepper flakes sounds wonderful!
This recipe is awesome! So much flavor!
Perfect casserole to get your veggies
For breakfast! Yum!
yes, a sneaky way of getting extra veg in the kiddos!
This sounds delicious. I have to try. Question – can this be made, put together the night before, refrigerated, and baked the next morning?
yes! Just pull it out of the oven 20-30 minutes before baking it.
I found this recipe when the brunch I was hosting jumped from 5 people to 16 ppl. I took a leap of faith to cook a recipe first time for such a large party (without trying it first). I made 2 batches and followed the recipe to the T, and this was a hit. I had leftover everything else but people loved this dish. I initially contemplated adding 1-2 more eggs and less cheese, but I’m so glad I didn’t and stuck to the recipe, it was perfection. I had to bake mine for an hour, but I have an older oven. Thank you for the detailed instructions and sharing such an amazing recipe! I will definitely be making this again!
So glad you liked it!
Delicious!! I do not cook often but since the family loved this casserole i’m inspired to cook more often. I’ll be returning to look for more recipes on your website. Thank you!!
thank you! glad it was a hit!
Can I make this the night before?
absolutely! I have assembled it the night before and then popped it in the oven in the next morning. Just be sure to add extra time baking or pull it out 30 minutes before you put it in the oven.
On taste, I rate this a 5 (though if I make it again I’ll use less or no added salt – the cheese is enough salty/savory flavor). My only “issue” is the prep time is NOT 15 minutes. Washing and cutting mushrooms alone is at least 5 minutes – unless you buy pre-sliced mushrooms, pre-shredded cheese etc. plan on an hour of prep time. (It is really tasty, though, for all the work.
Good points! I usually use pre-shredded cheese as it’s so easy to pick up a bag of sharp cheddar. I’ll make a note of that in the recipe!
Thanks for bringing it to my attention.
huge hit with the family last year, even those who love meat! will be making it for Christmas Eve brunch this year!
thanks so much!
This is a tried and true recipe! I’ve made it several times for different groups, always a success!
thank you!
I’ve been making this casserole for weeks now. I use 1 tbsp olive oil to cook the veggies and an olive oil spray for the pan to cut fat. I also add in a can of white beans. This is the protein rich breakfast of my dreams. Thank you!
Glad you liked it!
I make this recipe at least once a month! it’s delicious. it’s just my husband and I so I freeze individual portions, take one out the night before put in refrigerator and in the am reheat. very convenient and I get a serving of veggies first thing in the morning!
Thanks so much Tracy! I’m glad you like it!
Cynthia, you nailed it!!! This breakfast casserole is so moist and flavorful!! We had it for dinner and thoroughly enjoyed it! I added leftover broccoli, bell pepper, leek, dijon mustard and red pepper flakes. This recipe will be making future dates at our table!! i like the fact that it reheats very nicely, can be frozen and serves a group. Thank you very much for sharing it!!
That’s so nice to hear! Thank you!
If you cut the recipe in half for six servings, what size baking dish would you use? Can’t wait to try it, sounds delicious.
An 8″ x 8″ pan will work…it’ll be slightly more than half.
I’d use an 8×8″ square pan…It’ll be slightly too much filling, just cook it a bit longer.
This was absolutely delicious! A friend made it and gave me the recipe, then I made it tonight, and loved it. Prep time was a bit longer than stated, but worth it! I added two more eggs and it came out perfect. On your nutrition information it says serving size is 1g – what is that in ounces? I looked it up and google says 1/3 ounce – is that right? Thanks!
thanks! the default setting for the recipe card is “g” and I forgot to choose “serving” or “piece”. The nutritional info is one one serving. Can I ask how long it took you to prep it? I’ll make a note for next time I test it. Thank you, Cynthia
Thanks Cynthia for the serving size and for getting back to me! I’m pretty slow in prep time, but next time I will be faster… It probably took me about 25 minutes or so, chopping onions, slicing mushrooms, cooking them, then cooking the spinach. I forgot to say that I substituted ricotta for cottage cheese. sooo yummy. Had it again for lunch today.
you’re welcome!
Can I use frozen spinach?
if you use frozen spinach, make sure you defrost and get out as much liquid as possible.
Delicious! Modified with what I had on hand – 8 oz fresh spinach, 4 oz canned mushrooms (drained), combo of pepper jack and sharp cheddar, and added 1/2 cup pico de gallo. Will make again per the recipe (I’m sure it’ll be great!) or with the modifications!
thanks!
my favorite! moist, great flavors and easy to make.
thanks Cathy!