Go Back

Cheesy Yellow Squash and Zucchini Casserole

Cheesy yellow squash and zucchini casserole with a creamy vegetable filling and a golden buttery cracker topping. Sautéed squash and zucchini bake until bubbly, then rest for a sliceable, spoonable texture.
Print Recipe Pin Recipe
Prep Time 20 minutes
Cook Time 35 minutes
rest 10 minutes
Total Time 1 hour 5 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 420
Ingredients Equipment Method Notes

Ingredients
  

Casserole
  • 3 yellow squash
  • 3 zucchini
  • 1 onion
  • 2 tbsp butter plus extra for greasing if needed
  • 2 garlic
  • 1 tsp salt
  • 0.5 tsp black pepper
  • 0.5 tsp paprika
  • 1 cup sour cream
  • 1 cup shredded cheddar cheese
  • 0.5 cup grated Parmesan cheese
  • 2 large eggs
Topping
  • 1 cup buttery cracker crumbs
  • 2 tbsp melted butter
  • 0.25 cup Parmesan cheese

Equipment

  • 1 sheet pan
  • 1 cast iron skillet

Method
 

Preheat and prep
  1. Preheat the oven to 375°F (190°C). Set aside a 9×13-inch baking dish.
  2. Grease a 9×13-inch baking dish. Lightly coat the bottom and sides so the casserole releases easily.
Sauté the vegetables
  1. Melt butter in a large skillet over medium heat. Use enough heat to make the butter shimmer without browning.
  2. Sauté onion for 3 minutes. Stir until softened and translucent with a light golden edge.
  3. Add garlic, squash, and zucchini. Cook until the garlic is fragrant.
  4. Cook for 5–6 minutes until slightly softened. Keep stirring so the vegetables start to release moisture.
  5. Remove from heat and cool slightly. Let the skillet cool off so the egg mixture won’t scramble later.
Mix and assemble
  1. In a large bowl, combine sour cream, cheddar cheese, Parmesan, eggs, salt, pepper, and paprika. Stir just until smooth and evenly mixed.
  2. Stir in the cooked vegetables. Fold until the veggies are coated with the creamy mixture.
  3. Transfer the mixture to the baking dish. Spread into an even layer for consistent baking.
  4. Mix cracker crumbs, melted butter, and Parmesan. Stir until the crumbs look evenly moistened.
  5. Sprinkle evenly over casserole. Cover the surface so the topping turns golden as it bakes.
Bake and rest
  1. Bake for 30–35 minutes until golden brown and bubbly. The center should bubble and the edges should look set.
  2. Rest for 10 minutes before serving. Let it thicken slightly so portions hold their shape.

Notes

For the best texture, slice squash and zucchini evenly (about the same thickness) so they soften at the same rate. Refrigerate leftovers covered for up to 3 days. Freezing is not recommended because the creamy egg-and-cheese layer can weep when thawed. For a lighter option, use low-fat sour cream and reduce cheddar slightly while keeping the topping.