This delicious Zucchini Casserole is a cheesy, creamy, and comforting side dish made with fresh zucchini and yellow squash, mayonnaise, sour cream, panko breadcrumbs, and lots of cheese. It’s so easy to make and pairs perfectly with all your dinnertime favorites like chicken, beef, or fish.
Cheesy Zucchini Casserole
Whether you’re looking for exciting new ways to enjoy more greens and veggies, or you have a garden bursting with this yummy summer squash, you can’t go wrong with this cheesy cheddar and parmesan zucchini casserole recipe.
Zucchini, like cauliflower, is mild and super versatile, making it the perfect vegetable for casseroles, picky kiddos, or anyone hoping to fill their dinner plates with more greens.
Made with super simple ingredients like fresh zucchini, creamy mayonnaise, sour cream, and plenty of cheese, everyone will love this recipe – guaranteed! Serve it as a low-carb side dish with your favorite main dishes, or add it to your holiday meal plan.
Keto Zucchini Casserole
Is this recipe keto? Well, not quite. However, you can easily make it keto by skipping the panko breadcrumbs completely or replacing them with a keto-approved alternative like fried pork panko.
You may also like: Cheesy Cauliflower Bake with Bacon
How to Make Zucchini Casserole
1. Preheat the oven and spray a 1.5 quart (1.5L) casserole dish with non-stick cooking spray.
2. Prepare the zucchini: Zucchini is made up of 95% water. Unless we want a watery, mushy, soggy casserole, we need to salt and drain the zucchini for at least 30 to 45 minutes before cooking. Slice the zucchini into 1/4-inch rounds, toss in 1-2 teaspoons salt, and place in a colander set of the sink. After the zucchini has drained, transfer them to a clean kitchen towel lined with paper towels. Gently pat the zucchini dry.
3. Saute the onions: Cook the onions and garlic in butter or olive oil until softened.
4. Prepare the creamy cheese mixture: Combine the sour cream, mayonnaise, eggs, grated parmesan cheese, ½ cup of shredded cheddar cheese, and ½ cup of mozzarella cheese in a large bowl. Add the softened onions once cool, mixing well. Additional salt is not needed.
5. Assemble: Arrange the zucchini slices in overlapping rows (see image). Pour the creamy onion and cheese mixture over the top and smooth the surface with a wooden spoon.
6. Bake for 20 minutes, then carefully remove from the oven. Meanwhile, as the casserole is baking, melt the remaining two tablespoons of butter in a small bowl and combine with the panko breadcrumbs.
7. Top with the panko and cheese and bake again: Return the zucchini squash casserole to the oven and bake for an additional 20-25 minutes.
How to Serve
When serving this easy recipe to my family, I love to pair it with yummy main dish recipes like baked salmon or pan-seared steak. So cheesy and delicious, it doesn’t last long. It’s also great for holidays and family gatherings. In fact, it’s recently become a must-have addition to our Thanksgiving table.
Have you tried making this Zucchini Casserole Recipe?
Tell me about it in the comments below! I always love to hear your thoughts. And tag me #theforkedspoon on Instagram if you’ve made any of my recipes. I always love to see what you’re cooking in the kitchen.
- 4 medium zucchini squash - (sliced in 1/4" thick slices) see notes
- 4 tablespoon butter - divided
- 1 yellow onion - finely chopped
- 2 cloves garlic - minced
- ¼ black pepper
- ½ cup sour cream
- ½ cup mayonnaise
- 2 eggs - slightly beaten
- ½ cup grated parmesan cheese
- 1 cup shredded cheddar cheese - divided
- ½ cup shredded mozzarella cheese
- 1 cup panko breadcrumbs
- Preheat the oven to 375 degrees Fahrenheit. Spray a 1.5 quart (1.5L) casserole dish with non-stick cooking spray.
- Place the sliced zucchini in a large colander set over the kitchen sink. Toss the zucchini with salt (approximately 1-2 teaspoons). Drain the zucchini for at least 30-45 minutes. This step prevents us from ending up with a watery, soggy casserole. After the zucchini has drained, transfer them to a clean kitchen towel lined with paper towels. Gently pat the zucchini dry. Set aside.
- As the zucchini slices drain, soften the onions. Add two tablespoons of butter to a medium skillet set over medium heat. Add the onions and cook, often stirring to prevent burning, until the onions have softened. At the last minute, add the minced garlic and black pepper. Mix well to combine, then remove from heat. Set aside to cool completely.
- In a large bowl combine the sour cream, mayonnaise, eggs, grated parmesan cheese, ½ cup of shredded cheddar cheese, and ½ cup of mozzarella cheese. Once the onion and garlic mixture has cooled to room temperature, combine with the cheese mixture.
- Transfer the drained zucchini slices to the prepared baking dish. Arrange in several overlapping rows. Additional salt is not needed.
- Pour the creamy onion and cheese mixture directly over the top of the zucchini slices. Use a wooden spoon or spatula to smooth the surface.
- Transfer to the oven and bake for 20 minutes.
- Melt the remaining two tablespoons of butter in a small bowl in the microwave and combine with the panko breadcrumbs.
- Carefully remove the casserole from the oven. Top with the panko breadcrumbs and the remaining half cup of shredded cheddar cheese. Return to the oven to bake for an additional 20-25 minutes, or until the cheese is melted and bubbly and the breadcrumbs are golden brown.
- It is really hard to give an exact number of zucchini (or zucchini plus yellow squash) that you’ll need to make this casserole. At a minimum, you’ll need 4 medium-sized zucchini. I always make sure to have one extra squash on hand just in case.
- Leftovers: Keep leftovers stored in an airtight container in the refrigerator for up to 4 days. Reheat in the oven preheated to 350 degrees F or in the microwave until heated through.
- I do not recommend freezing.
- To make this recipe gluten-free, you may either omit the breadcrumbs or purchase breadcrumbs that are certified gluten-free.
(Nutrition information provided is an estimate and will vary based on cooking methods and specific brands of ingredients used.)