This easy Zucchini Casserole with Eggs and Cheese is one of my favorite ways to use summer zucchini. Made with fresh zucchini, eggs, mozzarella cheese, and simple pantry seasonings, this cheesy zucchini casserole is easy to prepare and works for breakfast, brunch, a side dish, or even a light dinner.
If your garden is overflowing with zucchini (or your mom's garden, in my case), this zucchini casserole recipe is a great way to use it up. The zucchini becomes tender while baking, and the eggs and cheese create a rich, satisfying texture that feels similar to a crustless quiche. It's simple, reliable, and made with everyday ingredients.
Why You'll Love This Egg Bake
- Simple ingredients: This recipe uses fresh zucchini, eggs, cheese, and pantry seasonings you may already have on hand.
- Great for garden zucchini: A practical way to use up an abundance of zucchini during the summer months.
- Make-ahead friendly: Bake it ahead of time and reheat slices throughout the week for easy breakfasts or lunches.
Jump to:
Ingredients
- Olive oil: Used to sauté the vegetables before baking.
- Zucchini: Fresh zucchini is the star of this casserole. Medium zucchini work best because they contain less moisture than oversized ones.
- Sweet onion: Adds mild sweetness and flavor.
- Eggs: The base of the casserole that holds everything together.
- Yellow mustard: Adds a subtle tang that complements the eggs and cheese.
- Mozzarella cheese: Creates a cheesy texture and helps bind the casserole.
- Seasoning: dried parsley, garlic powder, dried basil, dried oregano, salt, and black pepper.
See the recipe card for quantities.
Instructions
Preheat the oven to 400°F.
In a large skillet, heat olive oil over medium heat. Cook the onion and zucchini until the zucchini is tender and the onions are translucent. Drain in a colander and allow the veggies to cool for 5–10 minutes.
Tip: To soak up an excess liquid after draining, pat the zucchini dry with paper towels.
Meanwhile, whisk the eggs, mustard, shredded mozzarella, and seasonings until combined in a large mixing bowl.
When the zucchini has cooled slightly, stir the zucchini/onion mixture into the large bowl.
Grease a 9x13 casserole dish. Pour in zucchini/egg mixture. Smooth over the zucchini mixture so it lays flat. You want flat layers of zucchini.
Bake for 35 minutes or until eggs start to brown. Cover with foil and bake for an additional 10 minutes or until a knife is inserted into the center and comes out clean.
Let the cheesy zucchini breakfast casserole stand for 10 minutes before serving.
Substitutions and Variations
Here are a few ideas to remix this recipe to suit your taste (or your fridge contents!).
- Meat - this recipe would be absolutely delicious with the addition of sausage or bacon. For a casserole of this size, 1lb of breakfast sausage (cooked) or 5–6 slices of bacon (cooked) would be a good add-on.
- Cheese - I have made this with a blend of mozzarella and cheddar, and it turns out great. A little shredded parmesan cheese would be lovely, too.
- Mustard - you can absolutely use spicy mustard or brown mustard or whatever kind of mustard you prefer. The mustard adds a little zing to the egg bake.
- Seasoning - if you don't have basil and oregano, you could substitute these two with 2 teaspoon of Italian seasoning. To add some heat, add a pinch of red pepper flakes.
- Squash - yellow squash or any summer squash can be a good substitution, or it can be used alongside the zucchini slices.
- Garnish - visually take this dish to the next level with fresh parsley
If you're on the hunt for a vegan zucchini breakfast egg bake, try Minimalist Baker's Vegan Zucchini Gratin.
Behind the Recipe
Every summer I end up with more zucchini than I know what to do with thanks to my mom's green thumb. This zucchini casserole has become one of my favorite zucchini recipes because it uses simple ingredients and turns a pile of garden zucchini into something filling and satisfying.
My top tip is to remove as much moisture from the zucchini as possible. After cooking the zucchini mixture, let it drain in a colander and blot with paper towels if needed. This helps keep your zucchini casserole from becoming watery.
Another tip is to spread the zucchini mixture evenly in the prepared baking dish. Flat layers of zucchini help the casserole bake evenly from edge to center.
📖 Recipe
Zucchini Casserole with Eggs and Cheese
Ingredients
- 1 tablespoon olive oil extra virgin
- 8 cups thinly sliced zucchini about 6 medium
- 2 medium sweet onions sliced thinly
- 6 large eggs room temperature
- 1 tablespoon yellow mustard
- 4 cups shredded mozzarella cheese
- 1 tablespoon dried parsley flakes
- 1 teaspoon garlic powder
- 1 teaspoon dried basil leaves
- 1 teaspoon dried oregano leaves
- 1 teaspoon salt
- ½ teaspoon black pepper
Instructions
- Preheat oven to 400°F.
- In a large frying pan, heat olive oil over medium heat. Cook the zucchini and onion until the zucchini is tender and the onions are translucent. Drain in a colander and allow veggies to cool for 5–10 minutes.
- Meanwhile, whisk the eggs, mustard, shredded mozzarella, and seasonings until combined in a large mixing bowl. When the zucchini has cooled slightly, stir in the zucchini/onion mixture.
- Grease a 9x13 casserole dish. Pour in zucchini/egg mixture. Smooth over the zucchini so it lays flat.
- Bake for 30–35 minutes or until eggs start to brown. Cover with foil and bake for an additional 10 minutes or until a knife is inserted into the center and comes out clean.
- Let the casserole stand for 10 minutes before serving.
Notes
Nutrition
Food safety
- Cook to a minimum temperature of 160 °F (71.1 °C)
- Do not use the same utensils on cooked food, that previously touched raw egg
- Wash hands after touching raw egg or egg shells
- Do not eat raw eggs
- Don't leave food sitting out at room temperature for extended periods
- Don't leave cooking food unattended
See more guidelines at USDA.gov.
sylvia says
you need to state the weight of the zuccini as I have no idea what amount to slice.
Kelsey Smith says
Thanks for the feedback, Sylvia! I can definitely see how having a weight measurement would be helpful. You might try this recipe from The Kitchn or this recipe from Food Network.
Lindsay F says
Have you tried chopped zucchini and onion, instead of sliced?
Kelsey Smith says
Yes, the diced vegetables release a little more moisture during the sauté, so make sure to thoroughly drain and pat dry with paper towels. Other than that, you're good to go!
Allison says
This recipe did not look impressive to me off the ba, but it was outstanding! The seasoning mix is fantastic. I subbed half egg whites for half of the eggs and only used a quarter of the mozzarella cheese but it turned out really really well. Making again today.
Kelsey Smith says
So glad you loved it, and your swaps sound great. Thanks for sharing, and making it again is the best compliment.
Debbie says
I was looking for a way to use up some zucchini and came across this recipe. It was delicious, was great for food prepping lunches and my husband asked me to make it again!
Britny says
Will definitely be making this a lot!
Kelsey Smith says
Hey girl! Love to hear it.
Kelsey says
This recipe is also great as a quiche filling. Just pour it into two frozen crusts from the freezer section and bake on a sheet tray for the same amount of time.