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squash in a cheesy sauce on a plate garnished with parsley

Zucchini and Summer Squash with Mustard Sauce

Roasted Zucchini and Squash are covered in a creamy mustard sauce, topped with cheddar cheese and baked until gooey and delicious. This easy side dish is ready in under 30 minutes!

Course Side Dish
Cuisine American, French
Prep Time 10 minutes
Cook Time 30 minutes
Total Time 40 minutes
Servings 4 servings
Calories 89kcal


  • 2 small to medium sized summer squash
  • 2 small to medium sized zucchini squash
  • ½ cup Dijon mustard
  • 1 tbsp. Olive oil
  • ½ cup sharp cheddar cheese (6-8 oz.)


  • Preheat oven to 375 degrees. Slice zucchini and summer squash horizontally into thin strips (¼" thick).
  • Lightly salt and place in a colander for 10 minutes to draw out excess moisture. Dry with paper towels.
  • Drizzle about 1 teaspoon of olive oil in the bottom of a baking dish. Place one layer of squash in the bottom of the pan.
  • Spread a thin layer of Dijon mustard and a sprinkle of salt and pepper on top of the squash. Put another payer of squash, in a crisscross pattern. Cover with a thin layer of Dijon mustard, salt and pepper. Continue until all squash has been layered.
  • Drizzle olive oil on the top and place in oven. Bake for 20 minutes.
  • Remove from oven and sprinkle with cheese. Bake for another 10-15 minutes, or until cheese is bubbling and starting to brown.


  1. Lightly salt the zucchini and squash and let it sit in a colander 10 minutes before cooking. This helps draw out excess water so the zucchini and squash casserole doesn't come out watery. 
  2. If the cheese isn't brown enough, place it under the broiler for a couple minutes to let it get browned and bubbly. Watch it to make sure it doesn't burn.
  3. For best results, use a mandolin to slice the zucchini and squash into ¼" slices.


Serving: 6oz. | Calories: 89kcal | Carbohydrates: 6g | Protein: 5g | Fat: 5g | Saturated Fat: 3g | Cholesterol: 14mg | Sodium: 97mg | Potassium: 526mg | Fiber: 2g | Sugar: 4g | Vitamin A: 535IU | Vitamin C: 34.2mg | Calcium: 132mg | Iron: 0.8mg