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5 from 6 votes

Zucchini and Summer Squash Casserole

Cooking the squash in the skillet before assembly and baking adds flavor and more importantly, softens the squash so you can press out some of the moisture before baking. Even though the squash is browned in melted butter, when you press out the moisture, most of the butter goes with it so there's not much in the finished casserole.
Prep Time40 mins
Cook Time30 mins
Total Time1 hr 10 mins
Course: Side Dish
Cuisine: Casseroles
Servings: 8
Calories: 321kcal
Author: Good Dinner Mom


  • 3 tablespoons butter, plus softened butter for the baking dish
  • 1 large yellow onion, chopped
  • 4 garlic cloves, minced
  • 1 pound zucchini, cut into ½-inch rounds
  • 1 pound yellow squash, cut into ½-inch rounds
  • 1 cup fresh or frozen corn kernels
  • 2 cups shredded sharp cheddar cheese
  • 2 cups coarsely crushed buttery, flaky crackers, such as Ritz
  • 3 large eggs
  • 1 ½ cups whole milk
  • 3 tablespoons chopped fresh basil
  • 1 teaspoon kosher salt- if using table salt, add less
  • ½ teaspoon hot pepper sauce such as Tabasco
  • Freshly ground pepper, to taste
  • 2 Roma tomatoes, sliced thin


  • Position a rack in the center of the oven and preheat to 350F degrees. Lightly butter a 13x9-inch or large round (11-inch) baking dish.
  • Melt 1 tablespoon of the butter in a large skillet over medium-high heat. Add the onion and garlic. Cook, stirring occasionally, until tender and just starting to brown, about 10 minutes. Transfer the mixture to a medium bowl.
  • Melt another tablespoon of the butter in the skillet, again over medium-high heat. Add the zucchini in a single layer and cook, stirring occasionally, until browned and tender, about 5 minutes per side. Transfer the zucchini to a colander and let it drain over a plate or in your sink. Melt 1 more tablespoon of the butter and add the yellow squash in a single layer and cook in the same manner as the zucchini. Add the yellow squash to the zucchini in the colander. Using a rubber spatula, press gently on the squash mixture to remove excess moisture. Stir the squash into the onion mixture and add 1 cup of the cheddar.
  • Add the corn to this mixture.

Cook's Note:

  • Since the skillet is still warm, I like to toss the corn into it and quickly brown it on medium-high before adding, this adds nice flavor to the corn but is not critical.
  • Sprinkle 1 cup of the crackers in the bottom of the baking dish. Top them with the squash mixture.
  • Whisk the eggs in a medium bowl. Add the milk, basil, salt, black pepper, hot sauce and whisk until combined.
  • Pour the egg mixture evenly over the squash. Sprinkle the remaining 1 cup of cheddar over top, arrange the thinly sliced tomatoes over the cheese and then sprinkle the remaining 1 cup crackers over the tomatoes.
  • Bake until the casserole feels set when pressed gently in the center, about 30-35 minutes. Let stand for 5 minutes and serve.

Cook's Note:

  • You can substitute your favorite healthy oil for the butter, but the butter adds better flavor when browning plus remember you're pressing out a lot of it in the colander (do NOT use a butter substitute); I highly recommend using fresh basil and not omitting or substituting with dried, it makes a difference.


Calories: 321kcal | Carbohydrates: 21g | Protein: 14g | Fat: 21g | Saturated Fat: 10g | Polyunsaturated Fat: 3g | Monounsaturated Fat: 5g | Trans Fat: 0.3g | Cholesterol: 106mg | Sodium: 738mg | Potassium: 521mg | Fiber: 2g | Sugar: 8g | Vitamin A: 983IU | Vitamin C: 24mg | Calcium: 317mg | Iron: 2mg