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Overhead view of baked squash casserole showing a spoonful.

Summer Squash Casserole

Creamy, cheesy squash casserole with toasted buttery breadcrumbs, a comforting side dish that's perfect for using fresh summer yellow squash.
Course Side Dish
Cuisine American
Keyword Squash casserole, yellow squash casserole, with sour cream, with cheese
Prep Time 15 minutes
Cook Time 45 minutes
Total Time 1 hour
Servings 6
Author Kelly Wildenhaus | the hungry bluebird


  • tablespoons unsalted butter, divided
  • 1 small onion, finely diced
  • 1 pound yellow summer squash, thinly sliced about 3 medium squash
  • ½ cup grated Monterey Jack cheese
  • 1 egg, lightly beaten
  • ½ cup sour cream
  • 2 tablespoons dry white wine or vermouth
  • ½ teaspoon kosher salt
  • ½ teaspoon sugar
  • Dash or two hot pepper sauce
  • ½ cup fresh bread crumbs
  • 1 tablespoon chopped fresh parsley


  • Preheat oven to 350º.
    Melt 1 tablespoon butter in large skillet over medium-low heat. Add diced onion and cook until translucent, about 5 minutes. Transfer to small bowl and set aside.
  • Add 2 more tablespoons of butter to pan over medium-high heat and add squash. Cook and stir frequently until moisture has evaporated and squash is just tender, about 10 minutes. Transfer to a food processor and pulse until fairly smooth.
  • Transfer processed squash to a large bowl and add onions and all remaining ingredients except bread crumbs and parsley. Mix well and transfer to a small, round buttered baking dish.
  • Melt remaining 1½ tablespoons butter in a small saucepan over medium-high heat. Stir in fresh bread crumbs and cook and stir frequently until golden brown. Sprinkle over squash mixture. Bake for 30 to 35 minutes until hot and bubbly around the edges. Sprinkle with parsley and serve. Enjoy!