When summer gardens are overflowing with glossy green zucchini, there is no better way to honor the harvest than with a bubbling, golden-brown casserole of cheesy scalloped zucchini. This dish takes all the creamy, indulgent comfort of traditional scalloped potatoes and swaps in tender slices of summer squash, layered with a velvety cheese sauce and crowned with a buttery, crunchy topping. It is the kind of side dish that steals the show at potlucks, holiday dinners, and casual weeknight suppers alike—equally at home alongside a roasted chicken, a glazed ham, or even as a vegetarian main course with a crisp green salad.
For the Scalloped Zucchini
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3 to 4 medium zucchini (about 2 to 2 ½ pounds), sliced into ¼-inch rounds
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2 tablespoons unsalted butter, plus more for greasing the dish
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2 tablespoons all-purpose flour
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1 ½ cups whole milk or half-and-half, warmed
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1 ½ cups shredded sharp cheddar cheese, divided
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½ cup grated Parmesan cheese, divided
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1 small onion, thinly sliced or minced
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2 cloves garlic, minced
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½ teaspoon salt
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¼ teaspoon black pepper
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¼ teaspoon smoked paprika or ground nutmeg (optional, for warmth)
For the Topping
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½ cup panko breadcrumbs or crushed buttery crackers
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¼ cup grated Parmesan cheese
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2 tablespoons unsalted butter, melted
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Fresh thyme or parsley, chopped (for garnish)
Preparing the Zucchini
Preheat your oven to 375°F (190°C). Generously butter a 9×13-inch baking dish or a similar-sized shallow casserole dish.
Slice the zucchini into uniform rounds about a quarter-inch thick—this evenness is key to ensuring every layer cooks at the same pace. If your zucchini are particularly large or watery, you can lightly salt the slices and let them rest on paper towels for fifteen to twenty minutes to draw out excess moisture; simply pat them dry before assembling. This extra step helps prevent a watery casserole and concentrates the zucchini’s sweet, mild flavor.
Making the Cheese Sauce
In a medium saucepan over medium heat, melt the two tablespoons of butter. Add the sliced onion and cook, stirring occasionally, until it becomes soft and translucent—about five minutes. Stir in the minced garlic and cook for another minute until fragrant, being careful not to let it brown.
Sprinkle the flour over the onion and garlic mixture and whisk constantly for one to two minutes, allowing the flour to cook and lose its raw taste. Slowly pour in the warm milk or half-and-half while continuing to whisk, smoothing out any lumps as the mixture thickens into a silky béchamel. Reduce the heat to low and stir in one cup of the shredded cheddar and a quarter cup of the Parmesan, reserving the rest for later. Continue stirring until the cheese melts completely into the sauce, then season with salt, pepper, and your choice of smoked paprika or nutmeg. Taste and adjust the seasoning—the sauce should be rich and savory, as it will need to flavor all those layers of mild zucchini.
Assembling the Casserole
Spread a thin layer of the cheese sauce across the bottom of the prepared baking dish. Arrange a single layer of zucchini slices over the sauce, overlapping them slightly like shingles on a roof. Spoon another layer of sauce over the zucchini, then scatter some of the remaining shredded cheddar. Repeat this process—zucchini, sauce, cheese—until all the slices are used, finishing with a final layer of sauce on top. The dish should be generous and mounded slightly, as the zucchini will settle and release some liquid as it bakes.
In a small bowl, combine the panko breadcrumbs, the remaining quarter cup of Parmesan, and the melted butter, tossing until the crumbs are evenly moistened. Sprinkle this topping evenly over the casserole, creating a craggy, inviting crust.
Baking and Resting
Place the dish on a baking sheet to catch any drips, then bake uncovered for forty to forty-five minutes, or until the zucchini is tender when pierced with a knife and the sauce is bubbling and thickened around the edges. The topping should be deeply golden and crisp—if it needs a little more color, you can run it under the broiler for the final two minutes, watching it closely to prevent burning.
Once the casserole emerges from the oven, let it rest for at least ten minutes before serving. This resting period is essential; it allows the sauce to set up slightly, making it easier to scoop and serve cleanly, while also giving the flavors a moment to meld together beautifully.
Serving and Storing
Garnish the scalloped zucchini with a sprinkle of fresh thyme or parsley for a pop of color and brightness. Serve it warm as a comforting side dish alongside roasted meats, grilled sausages, or a simple roast chicken. Leftovers keep well in the refrigerator for up to three days and can be reheated gently in the oven or microwave—though in truth, this casserole rarely lasts long enough to see the inside of the fridge.
Cheesy, creamy, and crowned with a buttery crunch, this scalloped zucchini is the kind of dish that turns humble garden vegetables into something truly unforgettable.