There’s something truly comforting about a warm, cheesy dish that highlights fresh vegetables, and this decadent zucchini and yellow squash au gratin is exactly that. If you’re looking for a way to elevate your summer squash into a crowd-pleasing side, this zucchini au gratin recipe will become your go-to.
With its creamy sauce, tender slices, and crunchy golden topping, this dish is perfect for family dinners or potlucks. You’ll love how easy it is to prepare, yet so impressive on the table.
Why You'll Love This Recipe
- Rich and creamy texture that melts in your mouth
- Balanced flavors of fresh squash with sharp cheese
- Simple ingredients you likely have on hand
- Versatile side dish for any occasion
- Beautiful presentation that’s sure to impress
Ingredients
Gather these fresh ingredients to create a luscious zucchini au gratin that’s bursting with flavor.
- 3 cups thinly sliced zucchini (about 2 medium)
- 3 cups thinly sliced yellow squash (about 2 medium)
- 1 cup shredded sharp cheddar cheese
- 1 cup shredded Gruyère cheese
- 2 tablespoons unsalted butter
- 2 tablespoons all-purpose flour
- 1 ½ cups whole milk
- 1 teaspoon Dijon mustard
- ½ teaspoon garlic powder
- ½ teaspoon salt, plus more to taste
- ¼ teaspoon freshly ground black pepper
- ½ cup panko breadcrumbs
- 2 tablespoons grated Parmesan cheese
- 1 tablespoon fresh thyme leaves, chopped (optional garnish)
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Recipe Details
- Prep Time: 20 minutes
- Cook Time: 35 minutes
- Total Time: 55 minutes
- Servings: 6
- Calories: Approximately 280 per serving
How to Make Decadent Zucchini and Yellow Squash Au Gratin Recipe You’ll Love!
- Preheat your oven to 375°F (190°C) and lightly grease a 9x9 inch baking dish.
- In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes until it forms a smooth paste without browning.
- Gradually whisk in the milk, stirring constantly until the sauce thickens and coats the back of a spoon, about 5-7 minutes. Remove from heat and stir in the Dijon mustard, garlic powder, salt, pepper, and half of the shredded cheddar and Gruyère cheeses until melted and smooth.
- In your prepared dish, layer the zucchini and yellow squash slices evenly, then pour the cheese sauce over the top, pressing gently to submerge the slices.
- Mix the panko breadcrumbs with the Parmesan cheese and sprinkle evenly over the casserole. Top with the remaining cheddar and Gruyère cheeses for an extra cheesy crust.
- Bake uncovered for 30-35 minutes, or until the top is golden brown and bubbling, and the squash is tender when pierced with a fork.
- Remove from the oven and let it rest for 5 minutes before serving to allow the flavors to set.
- Garnish with fresh thyme leaves and serve warm as a delicious side dish.
Tips for the Best Results
- Slice the squash evenly to ensure uniform cooking and texture.
- Use whole milk for a richer cheese sauce; half-and-half works if you prefer creamier.
- Don’t skip the Dijon mustard—it adds a subtle depth to the cheese sauce.
- For a nuttier flavor, try substituting Gruyère with fontina or mozzarella.
- Let the dish rest before serving to thicken the sauce and enhance flavors.
Storage and Reheating
Store any leftover zucchini au gratin in an airtight container in the refrigerator for up to 3 days. To maintain the dish’s texture, reheat it covered in the oven at 350°F (175°C) until warmed through, about 15-20 minutes.
If you want to freeze the dish, wrap tightly in foil and freeze for up to 2 months. Thaw overnight in the refrigerator and reheat as directed, adding a few extra minutes if needed.
Frequently Asked Questions
Can I use other types of squash in this recipe?
Absolutely! Yellow squash and zucchini work beautifully together, but you can also add pattypan or even thin slices of summer pumpkin for variety. Just adjust cooking time if slices are thicker.
How do I prevent the dish from becoming watery?
Be sure to slice your squash thinly and evenly, and avoid overcrowding in the baking dish. The cheese sauce helps bind moisture, but resting the dish after baking lets excess liquid settle for perfect texture.
Can this recipe be made gluten-free?
Yes, simply substitute the all-purpose flour with a gluten-free flour blend and use gluten-free breadcrumbs. This will keep the creamy texture and crunchy topping intact.
Is it possible to prepare this dish ahead of time?
You can assemble the au gratin up to a day before baking. Cover and refrigerate, then bake it fresh when ready. This can help save time on busy days while still serving a fresh, warm dish.