Recipe

Cheesy Zucchini Casserole

Creamy, garlicky zucchini baked under a crisp, buttery breadcrumb topping. Cozy enough for Sunday, easy enough for Tuesday.

By Matt Campbell

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A golden-brown cheesy zucchini casserole in a white ceramic baking dish on a light kitchen counter, with a spoon lifting a creamy portion and a crisp breadcrumb topping

Jump to Recipe

Zucchini casserole is what happens when summer produce decides it wants to be comfort food. It is creamy, cheesy, and baked until the top gets those crisp little edges that you will absolutely “taste-test” straight from the pan.

This version keeps ingredients accessible and the steps low drama, but it still delivers real flavor: sautéed onion and garlic, a creamy binder that actually holds the zucchini together, and a buttery breadcrumb topping that crackles when you tap it with a spoon.

The only “serious” part is preventing the dreaded watery casserole situation. Do one small step with the zucchini (I will walk you through it) and the whole dish stays rich and cozy instead of soup-adjacent.

Whole zucchini, a yellow onion, garlic, shredded cheddar, sour cream, eggs, breadcrumbs, butter, and herbs arranged on a tidy kitchen counter in bright natural light

Why It Works

Not watery: We salt and drain the zucchini so the casserole bakes up creamy, not puddly.
Big flavor with simple ingredients: Onion, garlic, sharp cheddar, and Parmesan do the heavy lifting.
Perfect texture: Tender zucchini underneath, crisp buttery topping on top.
Flexible: Works as a side dish, a light vegetarian main, or a potluck pan that disappears fast.

Pairs Well With

Storage Tips

Refrigerate: Cool completely, then cover the baking dish or transfer to an airtight container. Keeps well for 3 to 4 days.

Reheat: For best texture, reheat in a 350°F oven until hot, about 15 to 20 minutes. Microwave works, but the topping will soften.

Freeze: You can freeze it, but quality can decline after thawing because zucchini tends to release extra water. If you do freeze, wrap tightly and freeze up to 2 months. Thaw overnight in the fridge and reheat uncovered in the oven to help evaporate moisture.

Common Questions

How do I keep zucchini casserole from getting watery?

Salt the sliced zucchini, let it sit 15 minutes, then squeeze it dry. I like using a clean kitchen towel for the squeeze. It is a tiny step that makes the final casserole creamy instead of runny. If it still looks a little loose, bake it 5 to 10 minutes longer uncovered and let it rest a bit longer before serving.

Do I peel zucchini first?

Nope. The peel is tender and adds color. If you are using giant late-season zucchini with tougher skin, you can peel a few strips off, but most grocery store zucchini do great unpeeled.

Can I make this ahead of time?

Yes. You have two good options: (1) Assemble the filling, cover, and refrigerate up to 24 hours, then add the breadcrumb topping right before baking for maximum crunch. (2) Assemble everything (including the topping) and refrigerate up to 24 hours, but know the panko will soften a bit. Bake as directed, adding 5 to 10 minutes if it is going in cold.

What cheese works best?

Sharp cheddar brings bite, Parmesan adds salty depth. You can swap in Monterey Jack, mozzarella, Gruyère, or pepper Jack. Just avoid super wet fresh mozzarella unless you drain it well.

Can I add protein?

Absolutely. Stir in cooked crumbled bacon, shredded rotisserie chicken, or browned Italian sausage. Keep it to about 1 to 1 1/2 cups so the casserole still portions neatly.

Is this gluten-free?

It can be. Use gluten-free breadcrumbs (or crushed gluten-free crackers) for the topping.

Matt Campbell

I have always had a huge passion for the culinary arts, people, working as a team, and so on. I wanted to pursue my love for cooking initially at Virginia Commonwealth University with a culinary arts degree; however, I instead decided to apply myself and acquire more practical skills. My end goal is to eventually open my own restaurant or similar establishment.

Kitchen Essentials

9x13-inch baking dish (or similar 3-quart casserole dish)
Large skillet
Colander
Mixing bowls
Whisk
Measuring cups and spoons
Clean kitchen towel or cheesecloth (for squeezing zucchini)

I used to think zucchini’s main personality trait was “polite.” It shows up, it behaves, it does not demand much. Then I started treating it like it wanted to be something more than a side vegetable and this casserole is the proof. You sauté the aromatics, you get the cheese involved, you give it a crunchy top, and suddenly zucchini is wearing a leather jacket and stealing the spotlight at dinner.

This is also one of my favorite “use what you have” pans. A couple extra zucchinis, half a bag of shredded cheese, some breadcrumbs hanging out in the pantry, and you are in business. It is the kind of food that feels like you tried harder than you did.

Cheesy Zucchini Casserole

( Reviews)

Prep Time 20 minutes

Cook Time 35 minutes

Total Time 55 minutes

Servings 8

Ingredients

2 1/2 pounds zucchini, sliced into 1/4-inch rounds (about 5 to 6 medium)
1 1/2 teaspoons kosher salt, divided
1 tablespoon olive oil
1 medium yellow onion, finely chopped
3 cloves garlic, minced
2 large eggs
1 cup sour cream
1/2 cup mayonnaise
2 cups shredded sharp cheddar
1/2 cup grated Parmesan
1/2 teaspoon black pepper
1 teaspoon dried Italian seasoning (or 1 tablespoon chopped fresh basil or parsley)
1 cup panko breadcrumbs
3 tablespoons unsalted butter, melted
Optional: pinch of red pepper flakes, 1 tablespoon chopped chives, or 1 to 2 teaspoons lemon zest

Sliced zucchini rounds sitting in a colander over a bowl, lightly sprinkled with salt on a kitchen counter, ready to drain

Instructions

Heat the oven. Preheat to 375°F. Lightly grease a 9x13-inch baking dish.
Drain the zucchini (this is the anti-soggy move). Put the sliced zucchini in a colander and toss with 1 teaspoon of the salt. Let sit for 15 minutes. Then squeeze it very dry using a clean kitchen towel or cheesecloth. At this volume, it is easiest to squeeze in 2 to 3 batches. You want “surprisingly dry,” not just “I dabbed it once.”
Sauté the flavor base. Heat olive oil in a large skillet over medium heat. Add onion and cook until soft, about 5 minutes. Add garlic and cook 30 seconds more. Take off the heat and let it cool for a minute so it does not scramble the eggs later.
Mix the creamy binder. In a large bowl, whisk eggs, sour cream, and mayonnaise until smooth. Stir in cheddar, Parmesan, black pepper, Italian seasoning, and the remaining 1/2 teaspoon salt (from the 1 1/2 teaspoons total).
Combine. Add the squeezed-dry zucchini and sautéed onion-garlic mixture to the bowl. Fold until everything is evenly coated.
Assemble. Spread the mixture into the prepared baking dish and level the top.
Top it. Stir panko with melted butter, then sprinkle evenly over the casserole.
Bake. Bake uncovered for 30 to 35 minutes, until bubbling around the edges and golden on top. If you want more crunch, broil for 1 to 2 minutes at the end on the upper rack, watching closely.
Rest, then portion. Let it sit for 10 minutes before serving. It sets up enough to portion neatly, but it is still creamy, so think tidy squares or hearty spoonfuls depending on your mood.