This zucchini egg bake is a perfect egg casserole recipe filled with cheese, zucchini sliced, and herbs. This cheesy breakfast casserole is low-carb, keto-friendly, gluten-free, and vegetarian, so it's a recipe that sure to please many diets.
Zucchini is in season from June through August, and it's one of my favorite summer vegetables. A simple egg casserole is one of my favorite zucchini recipes. Think of this as a crustless quiche.
My go-to breakfast recipe year-round is pancakes, but this savory summer dish is a seasonal favorite and an easy recipe to use up zucchini from the garden. This works whether you have giant zucchinis or small zucchini.
This post contains affiliate links. As an Amazon Associate, I earn revenue from qualifying purchases.
- Low carb: This recipe is perfect for a low-carb diet and a keto diet. See the recipe card for total carbohydrates and more nutritional data.
- Vegetarian: This meatless breakfast casserole is filled with mozzarella cheese, eggs, and zucchini.
This recipe calls for a few main ingredients (zucchini, onions, eggs, and cheese) and a beautiful blend of dried herbs.
- olive oil
- fresh zucchini
- sweet onion
- large eggs
- yellow mustard
- shredded mozzarella
- dried parsley
- garlic powder
- dried basil
- dried oregano
- black pepper
See the recipe card for quantities.
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 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.
This recipe calls for a 9x13 casserole dish. This is the perfect size baking dish for this recipe.
If you're in a pinch, I have also made this split across two 9-inch pie plates (same bake time), but it's slightly too much filling, so you would have to leave some out.
If you make this in a pie plate, I recommend putting the pie plate on top of a baking sheet to avoid a mess from overflowing.
Store cheesy zucchini egg bake covered in the refrigerator (baked) for three to four days or in the freezer (baked) for two to three months.
Reheat in the microwave in 30-second intervals.
Watch the eggs for browning. At the end of the first 30-minute cook time, keep an eye on the casserole. If they start to brown sooner, go ahead and add that foil over the top to prevent over-browning.
Lay the zucchini flat. Smooth the zucchini flat into the casserole dish for even baking.
Zucchini Egg Bake
- 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
- 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.
Bookmark this zucchini egg bake recipe, and tell me your favorite ways to use up zucchini.
- 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.
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!
Will definitely be making this a lot!
Kelsey Smith says
Hey girl! Love to hear it.
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.