The best dish to shine a spotlight on fresh summer produce! This cheesy Zucchini Gratin includes corn and sweet onions in a creamy sauce, plus gooey Gruyere cheese, crispy bread crumbs, and smoky bacon on top. The easy zucchini casserole is a simple side dish to serve with your favorite grilled chicken, salmon or steak, but it's also flavorful enough to stand on its own as an entrée with a side of crusty bread. If you have a bounty of zucchini in your garden, a delicious zucchini au gratin is the perfect way to enjoy it!
Zucchini au Gratin
While Zucchini Gratin or Zucchini au Gratin may sound fancy (thanks to its French name), this is really just a cheesy zucchini casserole! The word gratin means "a dish with a light browned crust of breadcrumbs or melted cheese," and that's exactly what we've got here. You'll cook the onion, zucchini and corn in butter and bacon drippings on the stovetop until tender, add flour and milk to make a creamy sauce, bake it in the oven, and finish it with Gruyere, homemade buttered breadcrumbs, and crispy bacon.
This easy recipe is a perfect summer side dish with fish or meat, or a light lunch or dinner when paired with a baguette. It's truly the best way to eat your veggies this season!
Ingredients
This is a quick overview of the ingredients that you'll need for a cheesy Zucchini Gratin recipe. As always, specific measurements and complete cooking instructions are included in the printable recipe box at the bottom of the post.
- Fresh breadcrumbs: tossed with butter and toasted in the oven for the best gratin topping!
- Bacon: adds a salty, smoky component to the dish that balances the sweetness of the corn and onion and provides depth of flavor.
- Butter: to sauté the vegetables and create the roux that thickens the cream sauce.
- Onion: for sweet, savory flavor.
- Zucchini and fresh corn: the vegetable base of the gratin.
- Kosher salt, freshly-ground black pepper, nutmeg and garlic powder: enhance the other flavors in the dish.
- All-purpose flour: to thicken the sauce.
- Whole milk: the liquid component of the creamy sauce. You can also use half-and-half or cream if you prefer.
- Gruyere cheese: a smooth-melting type of Swiss cheese. Substitute with regular Swiss cheese or even cheddar cheese, if you prefer.
The Bread Crumb Topping
Since buttered breadcrumbs are a hallmark of a good gratin, I prefer to make my own fresh bread crumbs at home. Nothing can compare, and in this case it's totally worth the extra few minutes of effort! A loaf of crusty sourdough yields a flavorful topping, but any rustic, hearty loaf will work.
To make ¾ cup fresh bread crumbs, start with about 1 ½ cups of cubed bread. Process the cubed bread in a food processor for about 30 seconds, or until it's the consistency of coarse crumbs.
How to Make Zucchini Gratin
Not just your average zucchini gratin, this dish features the added flavors of fresh, sweet corn off the cob and smoky, salty bacon. Best of all, the entire dish cooks in one skillet so that you have fewer dishes to wash at the end!
- Toss the bread crumbs with melted butter and toast in a 350° F oven until lightly browned, about 4 minutes.
- Cook the bacon in a cast iron skillet, then transfer to a paper towel-lined plate.
- Sauté the onion in the bacon drippings and melted butter until soft, about 10-12 minutes.
- Add the zucchini and corn, cover with a lid, and cook until the veggies are tender, about 10 minutes.
- Add the salt, pepper, nutmeg and garlic powder; cook for 1 more minute.
- Stir in the flour, cook for 1 minute, and then gradually add the cream.
- Simmer over low heat for 2-3 more minutes, or until the sauce thickens slightly.
- Sprinkle the cheese over top.
- Transfer the skillet to the oven and bake the gratin at 350° F for 20 minutes.
- Sprinkle the toasted breadcrumbs and the crispy bacon over top, and return the skillet to the oven for about 5 more minutes.
- Let the dish stand for 10 minutes before serving.
What to Serve with Cheesy Zucchini Gratin
This rich, decadent and easy zucchini casserole is a nice main course for lunch or dinner during the warm summer months. Pair it with a simple green salad dressed in balsamic vinaigrette and a side of crusty bread. We love this Dutch oven bread, this no-knead bread, or this easy baguette.
If you'd like to serve the zucchini au gratin as a side dish with a larger meal, try pairing it with any of these entrées:
- Grilled Salmon or Grilled Scallops
- Marinated Grilled Shrimp
- Grilled Chicken, Oven-Fried Chicken, Whole Roasted Chicken, or Roasted Chicken Thighs with Garlic and Herbs
- Grilled Flank Steak, Cast Iron Skillet Filet Mignon, or Grilled Steak Tips
- Grilled Pork Chops, Pork Tenderloin, or Pulled Pork
- Lemon Chicken Piccata, Pasta with Sausage and Spinach, or Shrimp Scampi
Storage
While it's best served warm straight from the skillet, you can store leftover gratin in an airtight container in the refrigerator for up to 3 days. Reheat in a 350° F oven just until warmed through. You can also reheat individual servings in the microwave.
I do not recommend freezing this dish, since the cream sauce may "break" when thawed and the thawed zucchini will water down the dish.
Recipe Variations
- While fresh sourdough breadcrumbs are the best, you can substitute with store-bought Panko breadcrumbs in a pinch.
- I prefer fresh corn cut off the cob; however, you can substitute with frozen corn when necessary. If using frozen corn, you don't need to add it to the skillet until the zucchini is almost tender, because the frozen corn will soften quickly.
- Swap out the zucchini (or some of the zucchini) for yellow squash.
- If using regular bacon instead of thick-cut bacon, increase it to 3 slices.
- Any good melting cheese will work for this recipe, so feel free to substitute with cheddar, Swiss, or Gouda in lieu of the Gruyere.
Tips for the Best Zucchini Gratin Recipe
- Use a mandoline to quickly cut the zucchini into even slices.
- Fresh corn cut off the cob is best for flavor and texture. I like to add some of the starchy liquid from the cob to the dish as well, which adds great flavor and helps to thicken the sauce a little bit.
- Use whole milk, half-and-half or cream -- do not substitute with a lower fat alternative. You need the fat in the milk to create a thick, rich sauce.
- Garnish with fresh herbs like thyme, parsley or chives for a bright and colorful finishing touch.
More Zucchini Recipes to Try
- Garlic Parmesan Zucchini Casserole
- Zucchini Fritters
- Greek Yogurt Chocolate Zucchini Cake
- Morning Glory Farm Zucchini Bread
- Skillet Pork Chops with Zucchini and Squash
- Crispy Zucchini Fries
- Easy Stuffed Zucchini Boats
Zucchini Gratin with Corn and Bacon
Ingredients
BREAD CRUMB TOPPING:
- ¾ cup fresh bread crumbs*
- 1 tablespoon salted butter, melted
FILLING:
- 2 slices thick-cut bacon, chopped
- 4 tablespoons salted butter
- 1 medium onion, thinly sliced
- 1 lb. zucchini, sliced ¼-inch thick (about 2 zucchini)
- 2 cups fresh corn kernels (about 3 ears)
- 1 teaspoon kosher salt, plus more to taste
- Freshly-ground black pepper, to taste
- ¼ teaspoon ground nutmeg
- ¼ teaspoon garlic powder
- 2 tablespoons all-purpose flour
- 1 cup whole milk or cream, at room temperature
- ½ cup grated Gruyere cheese
Instructions
MAKE THE BREAD CRUMB TOPPING:
- Preheat oven to 350° F. In a small bowl, toss together bread crumbs and melted butter. Spread on a baking sheet. Bake until lightly browned, about 4 minutes.
PREPARE THE FILLING:
- In a 10-inch cast iron skillet (or other oven-safe skillet), cook bacon over medium heat until crisp, about 6-8 minutes. Use a slotted spoon to remove bacon to a paper towel-lined plate, reserving the drippings in the pan.
- Add the butter to the skillet with the drippings. When the butter melts, stir in the onion and cook over medium-low heat until softened, about 10-12 minutes.
- Add the zucchini and corn, cover with a lid, and cook until tender, about 10 minutes. Add the salt, pepper, nutmeg and garlic powder; cook uncovered for 1 more minute.
- Stir in the flour and cook for 1 minute. Gradually add the milk or cream, stirring constantly. Cook over low heat for 2-3 more minutes, or until the sauce comes together and thickens.
- Sprinkle the cheese over top.
BAKE:
- Transfer the skillet to the 350° F oven. Bake (uncovered) for 20 minutes. Sprinkle buttered bread crumbs and bacon over top. Bake for 5 more minutes, or until the dish is bubbly.
- Let stand for about 10 minutes before serving.
Notes
- Use a mandoline to quickly cut the zucchini into even slices.
- Fresh corn cut off the cob is best for flavor and texture. I like to add some of the starchy liquid from the cob to the dish as well, which adds great flavor and helps to thicken the sauce a little bit.
- Use whole milk, half-and-half or cream -- do not substitute with a lower fat alternative. You need the fat in the milk to create a thick, rich sauce.
- Garnish with fresh herbs like thyme, parsley or chives for a bright and colorful finishing touch.
- While fresh sourdough breadcrumbs are the best, you can substitute with store-bought Panko breadcrumbs in a pinch.
- I prefer fresh corn cut off the cob; however, you can substitute with frozen corn when necessary. If using frozen corn, you probably don't need to add it to the skillet until the zucchini is almost tender, because the frozen corn will soften quickly.
- Swap out the zucchini (or some of the zucchini) for yellow squash.
- If using regular bacon instead of thick-cut bacon, increase it to 3 slices.
- Any good melting cheese will work for this recipe, so feel free to substitute with cheddar, Swiss, or Gouda in lieu of the Gruyere.
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