A comforting (but not coma-inducing) baked casserole of thinly sliced zucchini tossed in a creamy garlic sauce, then baked beneath a crown of golden, crispy breadcrumbs, easy, cheesy zucchini casserole gives a vegetable we usually think of as a straightforward side dish (Easy Sautéed Zucchini with Parmesan) the star holiday treatment usually reserved for Healthy Green Bean Casserole.
This old fashioned zucchini casserole recipe certainly stands to argue.
The sauce is herby and creamy, but light enough to where it doesn’t feel heavy on a hot summer night.
The buttery panko topping adds pleasing textural contrast. For an extra crispy zucchini casserole, place it under the broiler for an additional minute.
It uses a full two pounds of zucchini, making zucchini casserole an excellent thing to do with the extra zucchini you will inevitably have around this summer.
How to Make Zucchini Casserole
This simple zucchini casserole took me several tries to get right.
Zucchini has a high water content, and if you don’t find a way to remove the excess before baking it, you’ll end up with a soupy mess.
Many zucchini casserole recipes I found solved this issue by roasting the zucchini first.
While I love Roasted Zucchini, I was eager to skip the extra step and come up with the easiest zucchini casserole method possible (outside of Bisquick zucchini casserole that is. Homemade is the move here!).
I turned to the method I used for my Zucchini Ravioli: slice the zucchini thinly, sprinkle it with salt to draw out the extra water, then blot dry.
I’ve laid out the process in detail below to guarantee you easy zucchini casserole recipe success.
Zucchini. Often overlooked for the starring role, zucchini makes a fantastic base for this casserole. It becomes tender, soaks up the other flavors, and adds oodles of vitamin C, potassium, calcium, antioxidants, and fiber.
Salt. The key to achieving a non-soggy casserole.
Flour. Helps create a perfectly luscious and thick casserole.
Broth. Adds liquid and flavor to the casserole filling. You can use chicken or vegetable broth here.
Milk. I used 1% milk, but feel free to use whatever you have on hand.
PlainGreek Yogurt. Whole milk Greek yogurt is the right choice here rather than heavy cream. It adds richness and a subtle tanginess and won’t curdle when heated.
Cheese. I used both sharp cheddar cheese and Parmesan for the ultimate cheesy combo. The sharp cheddar is bold and deliciously melty, and the Parmesan adds an addictive salty, nutty flavor to the filling and topping.
Fresh Thyme. A delicious, fresh, herby complement to the creamy casserole filling.
You can also swap 1/3 the amount of dried thyme for fresh thyme.
Panko. Combined with Parmesan cheese and melted butter, panko bread crumbs create an exceptionally crispy and scrumptious casserole topping.
Zucchini Casserole with Meat
To make this an all-in-one meal with protein, stir in 1 pound of seasoned and sautéed ground chicken, turkey, or Italian sausage after adding the zucchini slices. Bake the casserole in a 9×13 inch pan and double the breadcrumb topping.
Slice the zucchini, then place it in a colander. Toss the zucchini with salt and let it drain.
Sauté the onion in a Dutch oven or high-rimmed skillet.
Stir in the flour.
Pour in the broth and milk. Let cook until the sauce thickens, then remove it from the heat.
Dry the zucchini.
Stir the yogurt into the onion mixture.
Add the cheddar.
Stir in the Parmesan and thyme.
Add the zucchini in small amounts, stirring frequently.
Stir in part of the panko, then transfer the mixture to a baking dish.
Melt the remaining butter, then stir in the remaining panko and Parmesan. Sprinkle the mixture over the top of the casserole.
Bake zucchini casserole at 400 degrees F for 30 to 35 minutes. Let rest for a few minutes, then DIG IN!
To Store. Place zucchini casserole in an airtight storage container in the refrigerator for up to 4 days.
To Reheat. Rewarm leftovers in a baking dish in the oven at 350 degrees F or in the microwave.
Meal Prep Tip
Cut the zucchini up to 1 day in advance. Refrigerate it in an airtight container until you’re ready to finish the recipe.
Stir diced or shredded Air Fryer Chicken Breast into the leftovers for a delicious meal. Serve as a side for Air Fryer Steak or other protein. You can also turn your leftovers into a vegetarian main by serving them over a bed of whole wheat pasta noodles.
fresh herbs for servinglike fresh parsley or basil, optional
Preheat the onion to 400 degrees F. Coat a 2 ½-quart baking dish (such as an 8×10-inch casserole dish) with nonstick spray.
Slice the zucchini crosswise into ¼-inch thick rounds (I find this quickest with a mandoline). Place in a large colander. Sprinkle with 1/2 teaspoon of the salt. Toss to coat the zucchini with the salt, making sure to separate the slices if needed. Place the colander over a large bowl (or in the sink, but don’t forget about it and accidentally turn on the water). Let drain at least 20 minutes.
Cut the onion in half through the stem ends, peel, and cut each half into thin, long strips.
In a Dutch oven or similar large, sturdy sauté pan, melt 2 tablespoons of the butter over medium heat. Add the onion, black pepper, and remaining 1/4 teaspoon salt. Sauté until the onion is beginning to soften and turn translucent, about 5 minutes. Stir in the garlic and let cook 30 seconds.
Sprinkle the flour over the top. Cook, stirring constantly, for 1 minute, until all of the flour turns golden and no white bits remain.
Slowly add the broth and milk a few splashes at a time, stirring between each addition to prevent lumps from forming. Increase the heat to medium high. Cook and stir, allowing the sauce to bubble, running a wooden spoon or spatula along the bottom of the pan. Continue cooking and stirring until the sauce reduces and thickens to resemble a very thick, creamy gravy, about 3 to 4 minutes. Remove from the heat.
Shake the colander to remove as much water as possible, then spread the zucchini onto paper towels or a clean kitchen towel. Blot dry, gently pressing out as much moisture as possible.
Stir the Greek yogurt into the sauce.
Add the cheddar cheese a few handfuls at a time, stirring between each addition to ensure it melts smoothly.
Stir in 2 tablespoons of the Parmesan and the thyme.
Add the zucchini by handfuls, stirring as you go to coat the slices evenly.
Stir in 1/4 cup panko, then transfer the mixture to the baking dish.
In a small bowl, melt the remaining 1 tablespoon butter. Add the remaining 1/4 cup panko and remaining 2 tablespoons Parmesan, stirring to combine. Sprinkle evenly over the casserole.
Bake the zucchini casserole until the filling is hot and bubbly and the zucchini is tender but not mushy, 30 to 35 minutes. If desired, switch the oven to broil to brown the top (watch carefully! You will only need a minute or so). Let rest at least 5 minutes, then enjoy.
TO STORE: Refrigerate casserole in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a baking dish in the oven at 350 degrees F or in the microwave.
Unfortunately, I don’t recommend freezing this casserole, as it will turn mushy and watery when thawed.