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The Parmesan and breadcrumb toppings add a delicious, golden-crispy topping to this healthy Zucchini Au Gratin recipe.

This zucchini au gratin is a healthier version of the classic dish, made without cream sauce and topped with a Parmesan breadcrumb topping that turns golden and crispy in the oven.

It’s a delicious way to use up an abundance of squash or make a low-carb alternative to potatoes au gratin that’s incredibly tasty.

healthy zucchini au gratin in an orange baking dish

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What is Au Gratin
Ingredients
How to Make Zucchini Au Gratin
Zucchini Au Gratin Recipe

And if the only au gratin you’ve ever had came from a box- 1.) My apologies 2.) This recipe will be a pleasant re-introduction.

The oven’s heat makes the squash tender, not mushy, while the topping gives each bite a cheesy, crisp texture.

Not to mention, this recipe has less than 4 grams of net carbs per serving- you could say it’s a keeper.

What is Au Gratin

The term au gratin describes a dish covered with breadcrumbs and cheese, then baked into a golden-brown crust.

Most of us are probably familiar with potatoes au gratin and have had it at least once, but in this recipe, I’m using the concept of ‘au gratin’ to transform zucchini.

You’ll also find many au gratin recipes made with a bechamel sauce or white sauce that consists of heavy cream, flour, and cheese. However, for the sake of simplicity and to keep this dish on the light side, we skip the sauce.

The topping gives the baked zucchini huge amounts of flavor, and eliminating the heavy sauce means one less thing for you to make tonight

Ingredients

Turn zucchini into this au gratin delight only takes a few simple staples. You’ll find the ingredient measurements in the recipe card at the end of the post, but first, let’s see what you need:

Zucchini or yellow squash: both are similar in flavor and texture, so you can swap one for the other without altering the outcome of this recipe.
Garlic: did anyone say epic flavor and aroma?
Olive oil: adds flavor and helps to stick the seasonings to the zucchini.
Seasonings: dried thyme, salt, and pepper.
Breadcrumbs: combined with the cheese, make a delicious breading! Use regular or gluten-free breadcrumbs.
Grated Parmesan: or another hard cheese, such as Asiago, Gruyére, or Pecorino Romano

dish of zucchini au gratin with pea & carrot ragout in the background

What is the Best Cheese to Use for Au Gratin

To create a good crust in au gratin, you want to use a hard cheese, like grated Asiago, Gruyére, Pecorino Romano, or plain ole’ grated Parmesan.

These cheeses and breadcrumbs achieve the ideal texture for the topping, but don’t stress if you don’t have the fancy stuff on hand- grated Parmesan works just fine.

Using Gluten-Free Bread Crumbs

You can also use gluten-free breadcrumbs to make this zucchini au gratin. I have a simple Panko breadcrumb recipe made with gluten-free rice cereal that has the crispy texture we love and makes a perfect all-purpose breadcrumb option.

Zucchini au gratin is also a favorite side dish for holiday menus and making it a gluten-free option ensures that everyone can have a bite. And if finding gluten-free recipes for Thanksgiving is a headache, check out my Giving Thanks: a Gluten-Free Menu.

It has 23 incredibly delicious recipes everyone will rave over and look forward to enjoying next year!

zucchini slices in an orange baking dish

How to Slice Zucchini Slices

For this au gratin, you’ll want the zucchini thinly sliced, about ½ to ¼-inch. By far, the easiest way to achieve thin, even slices is with a mandolin, but if you don’t have one, there’s no need to make a new purchase. A sharp chef’s knife and large cutting board will do the trick.

Trim the end
Place the zucchini on a large cutting board and use the knife to remove the stub of the stem.

Slice and repeat
Begin to slice the zucchini into ½ to ¼-inch thick slices, working away from your hand. Repeat with remaining zucchini.

How to Make Zucchini Au Gratin

Now that your zucchini is prepped and ready to go, let’s start on the rest of this recipe:

Prep
Position one oven rack on the lowest oven shelf and preheat to 450ºF. Lightly grease a 9 x 13-inch baking dish.
Bake the zucchini
Toss the zucchini with the oil and seasonings. Transfer to the prepared baking dish and bake until the zucchini is softened for about 15 minutes.
Make the breadcrumb topping
Meanwhile, in a separate large bowl, combine the breadcrumbs, Parmesan, and remaining oil.
Add the topping
Remove the baking dish from the oven and sprinkle the breadcrumb mixture over the zucchini.
Bake until golden brown and beautiful
Continue to bake until the cheesy topping is golden brown and crisp.

What to Serve with Zucchini Au Gratin

This zucchini au gratin is ideal as a side dish for dinner, and below I’ve included recipes to serve it with:

Zucchini Au Gratin Recipe

Servings: 6

Prep Time: 5

Cook Time: 30

The Parmesan and breadcrumb toppings add a delicious, golden-crispy topping to this healthy Zucchini Au Gratin recipe.

5 from 30 votes

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Ingredients

2 cloves garlic, minced
2 tablespoons extra-virgin olive oil, divided
1 teaspoon dried thyme
3 medium zucchini, thinly sliced
¼ teaspoon salt
¼ teaspoon freshly ground pepper
½ cup breadcrumbs*
½ cup grated Parmesan cheese

Instructions

Position one oven rack on the lower third shelf and preheat to 450F. Grease a 9 x 13-inch baking dish with olive oil or cooking spray.
In a large bowl, combine the garlic, 1 tablespoon of oil, thyme, salt, and black pepper. Add the zucchini and toss to coat with the seasonings.
Transfer to the greased baking dish and bake for 15 minutes or until the zucchini is softened.
Meanwhile, in a medium bowl, combine the breadcrumbs, Parmesan, and remaining oil. Whisk until the breadcrumbs are dampened and crumbly.
Using oven mitts, remove the baking dish from the oven and sprinkle the topping over the zucchini. Bake for an additional 15 minutes or until the topping is crisp.