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An overhead view of yellow squash casserole in a large black cast iron skillet.

Best-Ever Yellow Squash Casserole

Course: Side Dish
Cuisine: American, Southern, U.S.
Keyword: Baked squash, Summer Side Dish, Summer squash casserole
Prep Time: 15 minutes
Cook Time: 20 minutes
Total Time: 35 minutes
Servings: 12 people
Calories: 328kcal
Yellow Squash Casserol is a Southern U.S. staple side dish and is cheesy, creamy and loaded with summer squash taste. And what's even better, the dish is on the table from start to finish in less than 45 minutes!
Print Recipe


  • Mandolin, or sharp knife


  • 1 tbsp vegetable oil
  • 2 & 1/2 lbs yellow squashed sliced
  • 1 cup onion chopped
  • 8 oz. sour cream
  • 1/4 cup mayonnaise
  • 1 tsp Kosher salt
  • 1/2 tsp freshly ground black pepper
  • 1 1&2 cups cheddar cheese shredded
  • 1/2 cup Parmesan cheese grated
  • 1 large egg
  • 1 sleeve Ritz crackers crushed, but not completely pulverised
  • 2 tbsp unsalted butter melted


  • Pre-heat oven to 350°F. Lightly spray a 12-inch cast iron skillet or a 9"x9" casserole dish with cooking spray.
  • In a large skillet, heat the oil over medium-high heat. Add the sliced squash and onion and cook, stirring occassionally, until the vegetables have softened, about 10 minutes. Remove from heat and transfer to a colandar in the sink to drain.
  • In a large mixing bowl, stir together the sour cream, mayonnaise, salt, pepper, cheddar cheese, Parmesan cheese, and egg. Carfeully fold in the cooked squash mixture. Transfer to the prepared baking vessel.
  • In a separate medium bowl, use a fork to stir together the crushed crackers with the melted butter. Sprinkle the mixture all over the top of the casserole.
  • Bake for 25 minutes, uncovered, until bubbly and topping is starting to brown slightly. Remove and serve at once.



Be sure to slice the squash in uniform cuts.  1/4-inch slices are a good thickness.  A mandolin ensures even slicing, but a sharp knife and a steady hand will work just fine.
Don't over sauté the squash and onion.  Cook until just soft.  The vegetables will cook more once the casserole is in the oven.
The casserole can be assembled up to a day in advance and stored in the refrigerator.  Allow to come to room temperature before baking (about 1 hour on the counter), or add an additional 10 minutes to the bake time if no time for bringing to room temperature (total bake time will be 35 minutes).
This casserole is best served hot!


Calories: 328kcal | Carbohydrates: 4g | Protein: 33g | Fat: 52g | Saturated Fat: 32g | Cholesterol: 91mg | Sodium: 846mg | Potassium: 176mg | Fiber: 1g | Sugar: 2g | Vitamin A: 1462IU | Vitamin C: 1mg | Calcium: 958mg | Iron: 1mg