Cheesy Zucchini Casserole Recipe – Easy Side Dish
Add Preferred Source
Most zucchini casserole recipes skip the one step that decides whether you get a cheesy bake or a watery one, and it happens before the dish ever sees the oven. Zucchini is mostly water. Slice it, pour cheese over it, and all that water cooks straight out into the pan. Salting the slices first and blotting them dry is what keeps this zucchini casserole from turning to soup.
I make this through the back half of summer, when there’s more zucchini around than anyone knows what to do with. It’s a side that sits happily next to almost anything, and it holds together well enough to carry to a table where people are serving themselves.
Below is how I keep the slices from weeping, why the cheese mixture looks too thin before it bakes and why that’s fine, and the panko-and-butter topping that goes properly golden and crisp instead of soft.
This post contains affiliate links. As an Amazon Affiliate, if you purchase through those links, I earn a small commission. Thank you!
Why You’ll Love This Recipe
- The salting step does the heavy lifting. Fifteen to forty-five minutes with a little salt pulls the water out of the zucchini before it ever meets the cheese, so the finished dish sets instead of pooling.
- It uses egg and three cheeses to hold together rather than a heavy cream sauce, so it bakes up sliceable and rich with nothing to whisk on the stove first.
- The panko topping goes on partway through baking, not at the start, so it stays crisp and turns deep golden brown instead of steaming under the cheese.
- It’s built for a glut of garden zucchini. Four medium zucchini disappear into one small casserole dish, which is the fastest way I know to clear a countertop pile of them.
- You can freeze it before it’s baked, so it works as much for a make-ahead holiday side as it does for a Tuesday.
Ingredients You’ll Need
Zucchini. Use firm, medium zucchini, sliced a quarter-inch thick. I don’t use frozen zucchini here; it carries too much water and goes limp, and shredded gives you a denser, more custardy result than the sliced layers this recipe is after.
The three cheeses. Each does a different job. Sharp cheddar carries most of the flavor and gets divided, some into the mix, some on top. Mozzarella cheese is there for the melt and the pull. For the Parmesan, use a vegetarian one; most standard Parmesan is made with animal rennet, and the vegetarian versions grate and melt exactly the same way.
Eggs. Two eggs bind everything so the casserole slices instead of sliding apart. The cheese mixture looks thin when you pour it over the zucchini. That’s normal; the egg sets it as it bakes.
Panko breadcrumbs. Coarser and drier than regular breadcrumbs, which is why they crisp instead of turning to paste. Tossed with melted butter and a little extra Parmesan, they make the crunchy top layer.
How to Make Zucchini Casserole
A complete printable recipe and the measurements in both US customary and metric are available in the recipe card below.
Preparing Your Zucchini Slices
Preheat the oven to 375°F (or 190°C).
Start by salting the sliced zucchini in a colander and letting it sit for fifteen minutes at a minimum and closer to forty-five if you have the time, then blot it properly dry.
Mix the onion, eggs, all three cheeses, and the Italian seasoning in a big bowl and season it with salt and pepper. Layer the zucchini into a greased baking dish and pour the cheese mixture over the top. It bakes uncovered at 375°F for twenty minutes on its own first.
Then the panko breadcrumbs-butter-parmesan topping and the reserved cheddar go on, and it goes back in until the top is golden brown and bubbling, about another twenty minutes.
The one place people go wrong is rushing the salt; wet zucchini is the whole reason a casserole turns out watery.
Expert Tips for Zucchini Casserole
Salt the zucchini and mean it. Fifteen minutes is the floor, but thirty to forty-five pulls out noticeably more water, and you’ll see it bead up on the surface of the slices. Blot them dry with paper towels or a linen cloth; don’t rinse them, rinsing washes the seasoning off along with the water.
Trust the thin cheese mix. When you pour it over the zucchini, it looks too loose to set. The egg firms it in the oven, so resist the urge to add more cheese to thicken it; that just makes it greasy.
Add the topping halfway, not at the start. If the panko goes on before the casserole bakes, it sinks in and steams. Scattering it on after the first twenty minutes is what gets you a crisp, golden top.
Let it settle before you cut it. Five to ten minutes out of the oven lets the egg finish setting, so the first serving lifts out in a piece instead of sliding across the plate.
Ingredients
- 4 medium zucchini sliced into ¼" slices
- 1 pinch salt
- ½ cup onion finely chopped
- 2 eggs slightly beaten
- 1 cup sharp Cheddar cheese shredded and divided
- ½ cup mozzarella cheese shredded
- ½ cup vegetarian Parmesan cheese plus 2 additional tablespoons finely grated
- 2 teaspoons Italian seasoning
- Salt and pepper to taste
- 1 cup Panko breadcrumbs
- 2 tablespoons butter melted
Video
Instructions
- Preheat your oven to 375°F (190°C). Grease a 1 ½ quart casserole dish and set aside.
- Place the sliced zucchini in a colander lined with kitchen paper over the kitchen sink, lightly sprinkle with salt, and let it sit for a minimum of 15 minutes, but preferably 30 – 45 minutes. Transfer the zucchini slices to a dry kitchen towel or paper, and blot the slices dry as much as possible, then set aside.4 medium zucchini, 1 pinch salt
- In a large mixing bowl, combine onion, eggs, Cheddar cheese, mozzarella cheese, vegetarian Parmesan cheese, Italian seasoning, and salt and pepper to taste.½ cup onion, 2 eggs, 1 cup sharp Cheddar cheese, ½ cup mozzarella cheese, ½ cup vegetarian Parmesan cheese plus 2 additional tablespoons, 2 teaspoons Italian seasoning, Salt and pepper
- Place the zucchini in overlapping layers and pour over the cheesy mixture so the zucchini are covered.
- Bake uncovered for 20 minutes. Add Panko breadcrumbs to a small mixing bowl while it's baking, and pour over the melted butter, along with the additional vegetarian Parmesan cheese, and stir until it is fully combined.1 cup Panko breadcrumbs, 2 tablespoons butter
- Remove the casserole from the oven, sprinkle the breadcrumb mixture evenly over the top, and scatter the remaining shredded Cheddar cheese. Baked until the cheese has melted and is bubbling and the top is golden brown approximately 20 minutes.1 cup sharp Cheddar cheese
- Remove from the oven, serve and enjoy!
Notes
- Salt and blot the zucchini before assembling, this is what keeps the casserole from going watery.
- Store leftovers in an airtight container in the fridge for 3 to 4 days.
- To freeze, assemble unbaked, cover tightly, and freeze up to 2 to 3 months, then thaw before baking.
- Swap half the zucchini for yellow summer squash if you like.
- Reheat in the oven, not the microwave, so the panko topping stays crisp.
Nutrition
Variations
Mix in yellow squash. Swap half the zucchini for yellow summer squash. The dish looks brighter with the two colors layered together and the flavor stays mild and a touch sweeter.
Add some heat. A half teaspoon of crushed red pepper flakes stirred into the cheese mixture gives the whole thing a low background warmth against the cheese.
Fold in bell peppers. A handful of finely chopped bell pepper mixed in with the onion adds color and a little sweetness, and holds up fine through the bake.
What to Serve with Zucchini Casserole
This is a side, and it earns its place on a holiday table. It’s one of the vegetable dishes I’d put out at Thanksgiving alongside everything else, and in summer it does the same job at a more casual spread.
I usually keep what goes with it fresh and simple: a crisp Green Goddess Salad with the leaves dried well, and warm Homemade French Bread or crusty bread, to go with the cheese. When it’s the vegetable on a bigger vegetarian spread, it sits happily next to my Vegetarian Lasagne as the centerpiece.
How to Store Zucchini Casserole
Leftovers keep in an airtight container in the fridge for three to four days. Reheat in the oven or a toaster oven rather than the microwave, the panko goes soft in the microwave and crisps back up in dry heat.
To freeze, it’s better to freeze it before baking: assemble the whole dish, cover it tightly, and freeze for up to two to three months, then thaw and bake as written.
If you’re taking this to a summer cookout or potluck, keep an eye on the clock once it’s out, cooked food shouldn’t sit out longer than two hours, or one hour if it’s above 90°F outside.
More Zucchini Recipes to Try
Zucchini has a way of taking over the kitchen by mid-July. When a casserole isn’t what I’m after, these are the zucchini recipes I make next to keep up with the pile.
Zucchini Brownies are my sweet answer to a glut, all the chocolate up front with the vegetable tucked quietly inside.
Zucchini Muffins are what I bake for easy summer breakfasts, one more way to put the harvest to work.
Vegetable Fritters turn it savory and crisp, a good landing spot for the odds and ends at the bottom of the vegetable box.
Zucchini Casserole FAQs
Almost always it’s the zucchini going in wet. Salt the slices, let them sit at least fifteen minutes, and blot them dry before they go in the dish. That one step is the difference between a set casserole and a soupy one, and it’s the same move I use for my Spinach Casserole, another vegetable that holds a lot of water.
The best make-ahead route is to assemble it and freeze it unbaked for up to two to three months, then bake from thawed. I don’t love assembling it and leaving it in the fridge overnight, the salted zucchini keeps weeping and the dish can go watery. If you want to prep ahead, salt and blot the zucchini and mix the cheese separately, then combine and bake when you’re ready.
This recipe is built for fresh zucchini sliced into rounds. Frozen zucchini carries a lot of water, so if it’s all you have, thaw it and squeeze it very dry first. Shredded zucchini works but gives you a denser, more custardy result than the layered slices.
Four medium zucchini, which is what fills the small casserole dish this recipe uses. If yours are on the large side, use three and check the layers still fill the dish.
So, I’m not a big fan of zucchini. And I really don’t like hot zucchini. I mean, I’ll eat it, but it’s so not my fav. But my daughter LOVES it. And, if you’re a mid-life momma and your kiddo is coming to visit, you make her favorites even if you’re not a fan of zucchini. OMG, I LOVED this dish! The panko gave it a nice crunch (which got me past my usual complaint about baked zucchini being too mushy) and the cheese was, well, what is NOT better with cheese? Go ahead, I’ll wait while you think of something…
Made this twice. First as shown in recipe. Second I added ricotta and only added cheese on top, no breadcrumbs
Ricotta and skipping the breadcrumbs sounds like it’d bake up differently, more custardy than crusty on top. Might try that version myself, thanks for reporting back on both.