Summer Squash Casserole

Use fresh yellow crookneck squash for this dish. Zucchini also works well—or use a combination.

Serves: 4Hands-on: 25 minutesTotal: 1 hour 10 minutesDifficulty: Medium

Serves: 4


  • 2 lbs. yellow summer squash
  • 4 Tbsp. butter, divided
  • 1⁄2 cup chopped sweet onion
  • 4 oz. fresh button or cremini mushrooms, chopped
  • 3 1⁄2 Tbsp. all-purpose flour
  • 1 1⁄2 cups whole milk
  • 1 1⁄2 cups shredded mild Cheddar cheese
  • 2 Tbsp. chopped fresh flat-leaf parsley
  • 1⁄2 tsp. salt
  • 1⁄4 tsp. seasoned salt
  • 1⁄4 tsp. ground black pepper
  • 1⁄2 cup sour cream
  • 3⁄4 cup fine dry breadcrumbs


  • Cut squash into slices about 1⁄4 inch thick. Add to a large saucepan and cover with water. Bring to a boil over high heat. Reduce heat to medium; cover and simmer for 15 minutes until tender. Drain and set aside.
  • Preheat oven to 350°F. Lightly grease a 2-quart baking dish.
  • In a large saucepan, melt 3 tablespoons butter over medium-low heat. Add onion and mushrooms; sauté until tender. Add flour and stir until well incorporated. Gradually stir in milk. Continue cooking, stirring constantly, until thickened and bubbly. Stir in cheese, parsley, salt, seasoned salt, and pepper. Remove from heat. Taste and adjust seasonings. Stir in sour cream.
  • Combine squash and sauce. Pour mixture into the prepared dish. Toss bread crumbs with 1 tablespoon melted butter; sprinkle over squash mixture. Bake for 30 minutes or until browned and bubbly.