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+ servings

Zucchini Gratin with Corn and Bacon

This cheesy Zucchini Gratin includes corn and sweet onions in a creamy sauce, with Gruyere cheese, crispy bread crumbs, and smoky bacon on top. A light lunch or dinner, or a flavorful side dish!
Course Dinner, Lunch, Side Dish
Cuisine American, French
Keyword zucchini au gratin, zucchini gratin
Prep Time 15 minutes
Cook Time 1 hour 5 minutes
Resting Time 10 minutes
Total Time 1 hour 30 minutes
Servings 6 people
Calories 336kcal
Author Blair Lonergan



  • ¾ cup fresh bread crumbs*
  • 1 tablespoon salted butter, melted


  • 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



  • 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.


  • 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.


  • 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.


*To make ¾ cup fresh bread crumbs, start with about 1 ½ cups of cubed bread (I like to use a crusty loaf of sourdough bread). Process in a food processor until the cubes are coarse crumbs.
  • 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.


Serving: 1/6 of the recipe | Calories: 336kcal | Carbohydrates: 29g | Protein: 11g | Fat: 21g | Saturated Fat: 11g | Trans Fat: 1g | Cholesterol: 49mg | Sodium: 710mg | Potassium: 455mg | Fiber: 3g | Sugar: 8g | Vitamin A: 751IU | Vitamin C: 18mg | Calcium: 203mg | Iron: 1mg