Baked Zucchini Gratin Recipe with Parmesan Breadcrumbs

This baked zucchini gratin is a simple summer side dish that makes the most of fresh zucchini without much fuss. Thin slices of zucchini are layered in a baking dish with leeks, then topped with parmesan, breadcrumbs, and a drizzle of olive oil. After about 30 minutes in the oven, the zucchini is tender, the topping is golden, and the whole dish feels special without being hard to make.

It’s a lovely recipe for using garden zucchini, but it’s just as easy to make with a few small zucchini from the grocery store. Serve it with grilled chicken, baked fish, or a simple sandwich for a meal that feels fresh, easy, and homemade.

Quick Answer: To make baked zucchini gratin, layer evenly sliced zucchini in a greased gratin dish or pie plate with leeks, top with parmesan breadcrumbs, drizzle with olive oil, and bake at 400°F for about 30 minutes. Let it rest for 5 to 10 minutes before serving.

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What Is A Gratin?

A gratin is a baked dish with a golden, browned topping. The topping is often made with breadcrumbs, cheese, butter, or olive oil. Parmesan is a classic choice because it adds flavor and helps the top bake up crisp and golden. Underneath that topping, a gratin is usually made with thinly sliced vegetables, potatoes, or both. For this baked zucchini gratin, the zucchini slices are layered with leeks, then finished with parmesan breadcrumbs. The key is to slice the zucchini as evenly as possible, so the pieces bake at the same rate. You can arrange the zucchini in overlapping rows in a square baking dish, or spiral the slices in a round pie plate or gratin dish. Either way, the finished dish is simple, pretty, and perfect for serving right from the oven.

Ingredient Notes

• Zucchini: Fresh zucchini works best for this recipe. Choose small to medium zucchini that are firm, smooth, and about the same size, so the slices bake evenly. A mix of green zucchini and yellow squash is pretty, but all green zucchini works just as well. I do not recommend frozen zucchini for this gratin, because it releases too much moisture as it bakes.
• Leek: Leeks add mild onion flavor without overpowering the zucchini. Make sure to rinse the leek well after slicing, because dirt can hide between the layers. A sweet onion, green onion, or shallot can be used in place of the leek.
• Parmesan cheese: Parmesan gives the topping its salty flavor and helps it turn golden in the oven. Freshly grated parmesan is a good choice, but the kind from a container works too.
• Breadcrumbs: The breadcrumbs help form the crisp topping that makes this feel like a true gratin. Plain breadcrumbs keep the flavor simple, but seasoned breadcrumbs can also be used. If using seasoned breadcrumbs, you may want to go a little lighter on the garlic powder and parsley.
• Olive oil: Olive oil coats the zucchini slices and helps the parmesan breadcrumb topping brown. Use a light hand when drizzling it over the top, so the gratin does not become too oily.
• Garlic powder and parsley: These simple seasonings add flavor to the topping. Italian seasoning can be used in place of the parsley, or added along with it for a little more flavor.
• Baking dish: A shallow gratin dish, 9-inch pie plate, or 8×8 inch baking dish all work well. The zucchini slices should be layered, but not packed too tightly, so they have room to bake evenly.

How to Make Baked Zucchini Gratin

1. Preheat oven to 400°F.
2. Spray a ruffled pie plate or an 8×8 inch baking dish with non-stick spray and set aside.
3. Rinse and slice the leek thinly.
4. Slice the zucchini diagonally into 3/8-inch thick rounds.
5. In a large bowl, combine zucchini, leek, salt, pepper, and olive oil. Mix well.
6. In a separate small bowl, mix together the breadcrumbs, parmesan, garlic powder, and parsley.
7. Arrange half of the zucchini slices in a circular, overlapping pattern in the prepared pie plate.
8. Scatter the leeks between and under the zucchini slices as best you can.
9. Add a second layer of zucchini on top.
10. Sprinkle the breadcrumb mixture evenly over the zucchini layers.
11. Drizzle with a bit more olive oil.
12. Bake for 30 minutes. If the topping browns too quickly, loosely cover with foil.
13. Let the gratin rest for 5 to 10 minutes before serving.

How To Keep Baked Zucchini From Getting Watery

Zucchini naturally holds a lot of moisture, so a little extra care before baking can make a big difference. After slicing the zucchini, place the slices on a few layers of paper towel and gently blot the tops before adding them to the mixing bowl. This helps remove extra surface moisture without adding another step that takes too much time. Bake the gratin uncovered so some of the moisture can evaporate. If the parmesan breadcrumb topping gets golden before the zucchini is tender, loosely tent the dish with foil for the last few minutes. After baking, let the gratin rest for 5 to 10 minutes before serving. This gives the zucchini a chance to settle, and makes the dish easier to serve.

Serving Suggestions

This baked zucchini gratin is an easy side dish for summer meals, Sunday dinner, or any time you need to use up fresh zucchini. It goes especially well with grilled chicken, lemon chicken, baked fish, pork chops, or a simple sandwich. Because the parmesan breadcrumb topping adds so much flavor, you can keep the rest of the meal very simple. Add a tossed salad, sliced tomatoes, or fresh fruit, and dinner is ready without much extra work.

Tips, Substitutions, & Variations

• For the best baked zucchini gratin, choose small to medium zucchini or yellow squash that are firm and slender. Zucchini that is 2 to 2 1/2 inches in diameter works well. Extra-large zucchini can be watery, and the slices may not bake as evenly.
• Slice the zucchini as evenly as possible, about 3/8 inch thick. If the slices feel wet after cutting, place them on paper towels and gently blot before adding them to the mixing bowl.
• A leek adds mild onion flavor, but a sweet onion, green onion, or shallot can be used instead. A reader shared that she made this recipe with sweet onion in place of the leek, and gave it an A+.
• For a little more flavor, add extra garlic powder, a sprinkle of Italian seasoning, or a small amount of fresh thyme. Seasoned breadcrumbs can also be used in place of plain breadcrumbs.
• Keep an eye on the parmesan breadcrumb topping as the gratin bakes. If the top is golden before the zucchini is tender, loosely tent the dish with foil for the last few minutes.
• This recipe makes about 6 servings. For a smaller batch, cut the ingredients in half and prepare one layer of zucchini in a smaller baking dish.

Make Ahead, Store, & Reheat

• This baked zucchini gratin can be assembled earlier in the day. Cover the unbaked dish with foil or plastic wrap, and refrigerate until baking time. Before placing it in the oven, let the dish sit at room temperature for about 20 minutes so it bakes more evenly.
• This recipe is best served fresh from the oven, when the zucchini is tender and the parmesan breadcrumb topping is golden. If there are leftovers, cover the dish tightly or transfer the gratin to an airtight container. Store in the refrigerator for up to 3 days.
• To reheat, place the gratin in a 350°F oven until warmed through. The microwave can also be used for individual servings, but the topping will be softer. For the best texture, reheat uncovered in the oven or toaster oven.

Shop & Source

• ruffled pie dish
• glass mixing bowl set
• blue French stripe dish towel (similar)

This baked zucchini gratin is a simple way to turn fresh summer zucchini into a side dish that feels just a little special. The tender baked zucchini slices, mild leeks, parmesan cheese, and golden breadcrumb topping all come together with very little effort. When extra zucchini is on hand, there are so many easy ways to use it. For something sweet, try this moist zucchini bread or these easy zucchini muffins. For a hearty dinner idea, this zucchini lasagna is a wonderful way to add more vegetables to the table.