Old Fashioned Zucchini Casserole

An old fashioned zucchini casserole, cheesy, easy and delicious. This zucchini casserole with sour cream is creamy, rich and packed with flavor. Made with a crispy panko breadcrumb topping, this is irresistible! The perfect frozen zucchini recipe, or way to use up leftover zucchini.

Jump to:

• What makes this recipe so good?
• Ingredients you need for this old fashioned zucchini casserole:
• How to make this easy zucchini bake:
• How to keep squash casserole from getting watery:
• Is zucchini casserole a main dish or side dish?
• Storing leftovers:
• Freezing casserole:
• Recipe tips and tricks:
• Recipe FAQs:
• For more zucchini recipes:
• Old Fashioned Zucchini Casserole

What makes this recipe so good?

A cheesy baked zucchini casserole recipe is the definition of comfort food. The zucchini melts into the creamy cheese mixture, and the casserole is enhanced with the addition of panko bread crumbs and Parmesan cheese.

The flavors of a garlic parmesan zucchini casserole merge together so well. The garlic enhances the filling, and the Parmesan crisps up on top for a great textural contrast.

This is a great recipe to use up frozen zucchini, or leftover zucchini you have on hand. It comes together very simply with easy ingredients.

The method makes sure you won’t get overly soggy and watery zucchini, but a thick and cheesy casserole that you won’t be able to stop eating.

This is very low carb, you can even omit the panko breadcrumbs on the top to reduce the carb content even more.

This is a mayo and egg free zucchini casserole, so it doesn’t taste like a quiche like some other recipes.

Ingredients you need for this old fashioned zucchini casserole:

Unsalted butter: Both for sautéing the zucchini, and for tossing with the panko breadcrumbs to get a golden crispy top.

Onion and garlic: Perfect for infusing the zucchini with flavor.

Zucchini: You could use grated zucchini, or a mix of grated zucchini and sliced. I added just a little sliced zucchini to make the casserole look pretty, but this is totally optional. You could also use summer squash and make this into a wonderful squash casserole. You can use fresh zucchini, or grated zucchini that you have frozen and thawed. I actually used zucchini cores I had leftover from another recipe.

Italian seasoning, salt, and pepper: If you don’t have Italian seasoning on hand, feel free to substitute with dried basil, dried oregano or a mix of both.

Mozzarella and Parmesan cheese: This is what makes this into a zucchini mozzarella casserole, with the addition of the grated Parmesan on top. The mozzarella is mixed in for a cheesy, creamy filling. The Parmesan goes on top for a crispy salty topping. So good!

Olive oil: I like adding a little olive oil to give extra flavor to the panko topping, you could substitute with an additional tablespoon of melted butter.

Panko breadcrumbs: You can omit this for a gluten free zucchini casserole, or substitute for any other type of breadcrumb. I love the zucchini casserole with breadcrumbs, and the panko for the crispy texture they give this casserole. You can even substitute this with ritz cracker crumbs.

How to make this easy zucchini bake:

1. In a large skillet, add the 2 tablespoon of butter. Heat over medium heat, and once butter is melted, add the diced onion, garlic, zucchini, Italian seasoning, salt and pepper.
2. Saute for 6-8 minutes until softened and fragrant. If there’s a lot of extra liquid, drain it out.
3. Turn off the heat, and stir in the mozzarella cheese and sour cream. Mix until well combined, then transfer this mixture to a pyrex dish.
4. Melt the 1 tablespoon of butter and olive oil in the microwave. Add to the panko breadcrumbs, and toss to thoroughly coat.
5. Sprinkle the buttered panko breadcrumbs all over the top of the zucchini mixture in the casserole dish. Sprinkle with grated parmesan.
6. Bake for 20-25 minutes or until bubbling and golden brown. If you want a deeper color, you can turn the oven to broil for 1-2 minutes to crisp up the topping further.
7. Let casserole rest for 5-10 minutes, then serve while still hot. Enjoy!

How to keep squash casserole from getting watery:

The key is in the method. First of all, when you grate the zucchini, squeeze out as much excess water as you can from it.

Second of all, cook the liquid out. When sautéing and constantly stirring the zucchini or squash, liquid will release and the water will evaporate. If we put it in the oven raw, then all the water would release inside the casserole, and might lead to separation and mushiness.

After sautéing until softened, drain any excess liquid. Only at this point should you stir in the cheese and sour cream and proceed with the recipe.

Is zucchini casserole a main dish or side dish?

It can be either! I’ve enjoyed this very happily as a main dish. You could serve it with a simple green salad or crusty bread on the side.

You could also serve this as a side dish to roast chicken, turkey, meatloaf, steak, you name it!

Storing leftovers:

Leftover zucchini casserole will last 3-4 days tightly covered in the fridge. You can reheat it in a microwave, or in the oven.

Freezing casserole:

To freeze zucchini casserole, you can do it before you bake it or after. My preference would be before baking. Let the filling cool completely, then freeze with or without the panko topping. Tightly wrap in plastic wrap, then foil, and freeze for up to 3 months.

You don’t need to thaw before baking, but you can stick it in the fridge overnight to thaw if you want it to take up less time in the oven. If baking directly from frozen, you’ll have to add about 10 minutes or so extra time.

Recipe tips and tricks:

• Use any mix of zucchini you have on hand, it can be leftover zucchini cores from stuffing zucchini like in this recipe, or grated whole zucchini, or a mix of grated and sliced. I’d recommend a much bigger ratio of grated to sliced though, because the grated zucchini will melt in your mouth.
• Use summer squash and make this into a squash casserole! It’ll be delicious. I actually used Middle Eastern zucchini, which is very similar to squash (baby marrow).
• Use whole fat sour cream and cheeses, to get that super creamy and cheesy texture that this old fashioned zucchini casserole is famous for.
• You can alternately make this in a cast-iron skillet, so that you sauté the filling and bake the casserole in the same pan.

Recipe FAQs:

For more zucchini recipes:

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