Zucchini Gratin With Cheddar Cheese

zucchini gratin
Diana Rattray
  • Total: 45 mins
  • Prep: 20 mins
  • Cook: 25 mins
  • Yield: 6 servings
Nutritional Guidelines (per serving)
411 Calories
28g Fat
28g Carbs
15g Protein
See Full Nutritional Guidelines Hide Full Nutritional Guidelines
Nutrition Facts
Servings: 6 servings
Amount per serving
Calories 411
% Daily Value*
Total Fat 28g 35%
Saturated Fat 15g 76%
Cholesterol 72mg 24%
Sodium 840mg 37%
Total Carbohydrate 28g 10%
Dietary Fiber 3g 12%
Protein 15g
Calcium 381mg 29%
*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 zucchini gratin is a flavorful side dish casserole with extra richness from the cheddar cheese. A gratin is always a nice and relatively easy way to make a fancy side dish out of everyday vegetables. If you—or your neighbors—have an abundance of garden-fresh zucchini, this is an excellent way to use it.

The casserole is a good choice for a holiday meal or Sunday dinner, and it is a nice replacement for scalloped potatoes or mashed potatoes. 

The gratin is versatile as well. Make it with or without the crumbled cooked bacon or add even more richness with half-in-half or light cream instead of the milk. For a touch of garlic flavor, add about 1 teaspoon of finely chopped garlic to the skillet along with the zucchini. For the topping, instead of all cheddar, feel free to use a combination of cheddar and mozzarella cheese or another kind of melting cheese. Use part or all yellow summer squash if that's what you have on hand. 


  • 8 tablespoons butter (divided)
  • 1 large onion (chopped)
  • 2 pounds zucchini, sliced (approximately 6 cups)
  • 2 tablespoons all-purpose flour
  • 1 cup milk
  • 1 teaspoon kosher salt (or to taste)​
  • 1/4 teaspoon mustard powder
  • Black pepper (to taste)
  • Optional: pinch nutmeg
  • Optional: 4 strips bacon (cooked until crisp, drained and crumbled)
  • 1 cup shredded cheddar cheese
  • 1 cup breadcrumbs (soft, fresh)

Steps to Make It

  1. Heat the oven to 350 F.

  2. Butter a 1 1/2-quart baking dish.

  3. In a large skillet over medium heat, melt 4 tablespoons of butter. Add the chopped onion and saute, stirring, until it is tender and translucent.

  4. Add the sliced zucchini to the skillet and reduce the heat to low; cover the pan and cook for 10 to 15 minutes, or until just tender. Remove the vegetables to a bowl with a slotted spoon and set aside.

  5. Add 2 tablespoons of butter to the skillet and melt over medium-low heat. Add the flour and cook, stirring constantly, for 2 minutes. Gradually add the milk to the flour and butter roux and continue cooking until thickened, stirring constantly. Add the kosher salt, mustard powder, and freshly ground black pepper, along with a dash of nutmeg, if desired. 

  6. Taste the sauce and adjust the seasonings, as needed.

  7. There will be some excess liquid from the cooked zucchini, so use a slotted spoon to transfer the zucchini and onions back to the skillet. Stir the mixture gently to coat the zucchini with the sauce. 

  8. Turn the zucchini and sauce mixture into the prepared baking dish. 

  9. Sprinkle the shredded cheese over the casserole along with the cooked crumbled bacon, if using.

  10. Melt the remaining 2 tablespoons of butter and toss with the breadcrumbs. Sprinkle over the zucchini casserole.

  11. Bake the gratin in the preheated oven for 20 to 25 minutes, or until the topping is browned and the casserole is bubbling around the edges.