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summer squash gratin

Summer Squash Gratin

This creamy and cheesy summer squash gratin transforms humble garden vegetables into a showstopping dish with its golden topping. It's the ultimate comfort food that celebrates summer's bounty and will convert even vegetable skeptics.
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Course: Side Dish
Cuisine: American, French
Keyword: Summer Squash, Gratin, Zucchini, Vegetable Side Dish, Cheesy Vegetables
Prep Time: 20 minutes
Cook Time: 40 minutes
Draining Time: 15 minutes
Total Time: 1 hour
Servings: 8 servings
Calories: 285kcal

Equipment

  • 9x13 inch Baking Dish
  • Mandoline Slicer (optional)
  • Colander
  • Skillet

Ingredients

Base Ingredients

  • 2 pounds mixed summer squash (zucchini, yellow squash) thinly sliced
  • 1 large sweet onion thinly sliced
  • 3 cloves garlic minced
  • 2 tablespoons olive oil
  • 2 tablespoons fresh thyme leaves or 2 teaspoons dried
  • 1 cup heavy cream substitute: full-fat coconut milk for dairy-free option

Cheese & Topping

  • 1 cup Gruyère cheese grated (substitute: dairy-free cheese or nutritional yeast)
  • 1/2 cup Parmesan cheese grated
  • 1/2 cup panko breadcrumbs
  • 2 tablespoons butter melted (substitute: olive oil)
  • salt and freshly ground black pepper to taste

Instructions

  • Slice your summer squash into uniform 1/4-inch rounds. Toss the sliced squash with 1 teaspoon of salt in a colander and let sit for 15 minutes to draw out excess moisture.
  • In a large skillet, heat olive oil over medium heat. Add onions and cook until translucent, about 5 minutes. Add garlic and thyme, cooking for another minute until fragrant.
  • Preheat your oven to 375°F (190°C). Pat the squash dry with paper towels. In a 9x13-inch baking dish, arrange half of the squash in overlapping layers. Season with pepper and sprinkle with 1/3 of the cheese mixture.
  • Add the onion mixture as the next layer.
  • Add remaining squash in an attractive pattern (concentric circles work beautifully) and pour the cream evenly over the top.
  • Mix the remaining cheeses with panko breadcrumbs and melted butter. Sprinkle this mixture evenly over the top of the gratin.
  • Bake uncovered for 35-40 minutes until the top is golden brown and the casserole is bubbling around the edges. Let stand for 10 minutes before serving.

Notes

Don't skip salting and draining the squash—this step reduces excess moisture by up to 30%, preventing a soggy gratin.
Using a mandoline will ensure even cooking and a professional presentation.
For make-ahead preparation, assemble the gratin up to 24 hours ahead, cover and refrigerate. Add 10-15 minutes to the baking time if cooking from refrigerated.

Nutrition

Calories: 285kcal | Carbohydrates: 12g | Protein: 9g | Fat: 23g | Sodium: 310mg | Fiber: 2g
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