Yellow Squash Casserole

Squash casserole with cheese and breadcrumb topping

The Spruce / Diana Rattray

Prep: 15 mins
Cook: 30 mins
Total: 45 mins
Servings: 4 servings
Nutritional Guidelines (per serving)
496 Calories
44g Fat
12g Carbs
14g Protein
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Nutrition Facts
Servings: 4
Amount per serving
Calories 496
% Daily Value*
Total Fat 44g 56%
Saturated Fat 19g 94%
Cholesterol 229mg 76%
Sodium 492mg 21%
Total Carbohydrate 12g 4%
Dietary Fiber 1g 5%
Protein 14g
Calcium 276mg 21%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)

This yellow summer casserole is a favorite all year round, great for family meals during the summer but also popular for holiday dinners, especially in the South. 

You can use yellow summer straightneck or crookneck squash or make the casserole with zucchini or another type of summer squash. It's a great way to use zucchini or summer squash when you are enjoying nature's bounty from your garden (or your neighbor's garden).

Zucchini and summer squash are abundant during the summer months because they are easy to grow and mature relatively quickly. If you are growing it in your garden, you'll need plenty of recipes to use it. If one of your solutions is to share your squash with friends, family, and co-workers, include a link to this recipe.

The recipe is easily scaled up for a potluck dish or large family dinner.


  • 2 medium yellow summer squash (about 2 cups, seeds removed, cooked, drained, and mashed squash; no need to peel)
  • Kosher salt (to taste)
  • Freshly ground black pepper (to taste)
  • 1 small onion
  • 1/2 cup mayonnaise
  • 1 large egg
  • 1 teaspoon sugar
  • 4 tablespoons melted butter (divided)
  • 3/4 cup shredded Cheddar cheese (divided)
  • 1 cup breadcrumbs (fresh, finely ground)

Steps to Make It

  1. Gather the ingredients.

  2. Heat the oven to 350 F. Butter a 1-quart casserole or baking dish. 

  3. Slice the summer squash and place it in a medium saucepan. Cover the squash with water and add 1 teaspoon of salt. Place the pan over high heat and bring the squash to a boil. Reduce the heat to medium-low and cover the pan; continue to cook until tender, or for about 10 to 15 minutes.

  4. Meanwhile, peel the onion and cut it into halves; chop it finely.

  5. Drain the squash thoroughly; return it to the saucepan and mash it. Taste the squash and add salt and pepper, as desired.

  6. In a bowl, whisk the egg and sugar lightly. Add the mayonnaise, chopped onion, 2 tablespoons of the melted butter, and 1/2 cup of the cheddar cheese. Stir to blend thoroughly.

  7. Blend the mashed squash into the egg and mayonnaise mixture.

  8. Spoon the mixture into the prepared casserole.

  9. Top the casserole with the remaining 1/4 cup of shredded cheese.

  10. Toss the breadcrumbs with the remaining 2 tablespoons of melted butter and then sprinkle them over the casserole.

  11. Bake for 30 minutes, or until bubbly and lightly browned.

  12. Serve squash casserole hot.


  • This casserole is a good side dish that can take the place of a heavier starch, and it goes well with just about any protein, especially chicken or fish. If you're serving fried chicken, roasted chicken, or grilled chicken breast, it will pair very well. It will also pair well with grilled or baked fish, including salmon. A fresh green salad will complement the meal.

Recipe Variations

  • Variations include adding chopped red peppers or green peppers with the onion, adding a little color as well as their flavor. You can spice it up by adding chilies as well.