A creamy, cheesy baked zucchini casserole with tender zucchini, garlic, herbs, and a golden melted-cheese topping. It’s an easy side dish that works beautifully with chicken, fish, beef, or a simple salad.

 Ingredients

For the Casserole

• 4 medium zucchini, about 2 lb (900 g)
• 1 small yellow onion, finely diced
• 3 cloves garlic, minced
• 1 tablespoon olive oil
• 1/2 teaspoon salt, plus more for zucchini
• 1/2 teaspoon black pepper
• 1 teaspoon Italian seasoning
• 1/2 teaspoon dried oregano
• 2 large eggs
• 1/2 cup (120 g) sour cream
• 1/2 cup (120 ml) heavy cream or whole milk
• 1 cup (100 g) shredded mozzarella cheese
• 1/2 cup (50 g) shredded cheddar cheese
• 1/4 cup (25 g) grated Parmesan cheese

Optional Topping

• 1/2 cup (50 g) shredded mozzarella
• 2 tablespoons grated Parmesan
• 2 tablespoons breadcrumbs for extra crunch
• 1 tablespoon chopped fresh parsley

Detailed Instructions

1. Preheat the oven

Preheat your oven to 375°F (190°C).

Lightly grease a 9 × 13-inch (23 × 33 cm) baking dish with olive oil or cooking spray.

2. Prepare the zucchini

Wash and dry the zucchini.

Slice into thin rounds, approximately 1/4 inch (6 mm) thick.

Place the zucchini in a colander and sprinkle lightly with salt. Let it sit for 10–15 minutes.

Zucchini contains a lot of water, so this step helps reduce excess moisture.

Pat the zucchini thoroughly dry with paper towels or a clean kitchen towel.

3. Sauté the onion and garlic

Heat 1 tablespoon olive oil in a large skillet over medium heat.

Add the diced onion and cook for 3–4 minutes, until softened.

Add the minced garlic and cook for another 30–60 seconds.

Remove from the heat.

4. Make the creamy mixture

In a large bowl, whisk together:

• Eggs
• Sour cream
• Heavy cream or milk
• Italian seasoning
• Oregano
• Black pepper

Mix until smooth.

5. Add the cheeses

Stir in:

• 1 cup mozzarella
• 1/2 cup cheddar
• 1/4 cup Parmesan

Reserve a little mozzarella and Parmesan for the top.

6. Combine everything

Add the drained zucchini and sautéed onion mixture to the bowl.

Gently stir until the zucchini is evenly coated with the creamy cheese mixture.

7. Transfer to the baking dish

Spread the mixture evenly into the prepared baking dish.

Sprinkle the remaining mozzarella and Parmesan over the top.

For a crispy topping, add breadcrumbs if desired.

8. Bake

Place the casserole in the preheated oven.

Bake for approximately 30–40 minutes, until:

• The zucchini is tender.
• The center is set.
• The cheese is melted.
• The top is golden brown.

If you want a more deeply browned top, switch to the broiler for 1–2 minutes at the end, watching carefully.

9. Rest

Remove from the oven and allow the casserole to rest for 10 minutes.

This helps it set and makes it easier to serve.

10. Garnish and serve

Sprinkle with fresh chopped parsley and serve warm.

Tips for the Best Zucchini Casserole

Don’t skip draining the zucchini. Excess water can make the casserole watery.

Don’t slice the zucchini too thin. Very thin slices can become overly soft during baking.

Use freshly shredded cheese when possible. It usually melts more smoothly than pre-shredded cheese.

Don’t overcrowd the baking dish. An even layer helps the casserole cook consistently.

Let it rest before serving. The cheese mixture becomes firmer as it cools slightly.

 Easy Variations

Cheesy Bacon Zucchini Casserole

Add 1/2 cup cooked and crumbled bacon before baking.

 Zucchini & Tomato Casserole

Add thinly sliced tomatoes, but pat them dry first to reduce excess moisture.

Spicy Version

Add 1/4 teaspoon red pepper flakes or a small amount of diced jalapeño.

 Mediterranean Style

Add chopped parsley, oregano, a little feta, and sliced olives.

 Extra Garlic

Add another clove of garlic or use roasted garlic for a sweeter flavor.

Nut Information

The recipe is nut-free as written.

There are no peanuts or tree nuts required.

This includes no:

• Almonds
• Walnuts
• Pecans
• Cashews
• Pistachios
• Hazelnuts
• Macadamia nuts

If you have a nut allergy

Check packaged ingredients such as:

• Shredded cheese
• Breadcrumbs
• Sour cream
• Cream
• Seasoning blends

Look for allergy statements and avoid cross-contact with utensils, cutting boards, baking dishes, or surfaces that have been used with nuts.

Dairy note: This recipe contains several dairy ingredients. Dairy is not a nut, but the casserole is not dairy-free.

 Cheesy Zucchini Casserole Q&A

Can I make this casserole ahead of time?

Yes. Assemble it, cover it, and refrigerate it before baking. When ready to cook, allow the cold dish to sit out briefly while the oven preheats, then bake until completely hot and set.

Why is my zucchini casserole watery?

Zucchini naturally contains a lot of water. Salting, resting, and thoroughly drying the zucchini before assembling the casserole helps significantly.

Can I skip the sour cream?

Yes. Plain Greek yogurt can be used as a substitute.

Can I use milk instead of heavy cream?

Yes. Whole milk will make the casserole slightly lighter and less rich.

Can I use only mozzarella?

Yes. Mozzarella works well on its own, although adding cheddar or Parmesan gives the casserole more flavor.

Can I use Parmesan instead of cheddar?

Yes. You can adjust the cheese combination according to your preference.

Can I make it without breadcrumbs?

Absolutely. Breadcrumbs are optional and are only used for extra crunch.

Can I use frozen zucchini?

Fresh zucchini is recommended. Frozen zucchini can release considerable moisture and may make the casserole watery.

Can I add meat?

Yes. Cooked chicken, turkey, ground beef, or bacon can be added. Make sure any meat is fully cooked before combining it with the casserole.

Can I make it vegetarian?

Yes. The recipe is vegetarian as written.

Is it gluten-free?

The main casserole ingredients can be gluten-free, but breadcrumbs may contain gluten. Use certified gluten-free breadcrumbs if needed, and check all packaged ingredients.

Can I make it dairy-free?

Yes, but you would need dairy-free substitutes for the sour cream, cream, mozzarella, cheddar, and Parmesan. The final texture may differ.

Can I freeze it?

You can, although zucchini may become softer after thawing. For the best texture, freezing is generally less ideal than eating it fresh or refrigerated.

How should I store leftovers?

Place cooled leftovers in an airtight container and refrigerate.

How long do leftovers last?

For best quality, enjoy refrigerated leftovers within 3–4 days.

How should I reheat it?

Reheat individual portions in the microwave or warm the whole casserole in a 350°F (175°C) oven until heated through.

What can I serve with it?

It pairs well with:

• Roast chicken
• Grilled chicken
• Baked fish
• Turkey
• Steak
• Rice
• Green salad
• Roasted potatoes

Recipe at a Glance

Prep: 20 minutes
Bake: 30–40 minutes
Rest: 10 minutes
Total: About 1 hour
Servings: 6–8
Difficulty: Easy
Best served: Warm