This delicious Zucchini Au Gratin Recipe is a great rice based side dish that’s perfect to serve throughout the holidays.  This amazing zucchini casserole is deliciously cheesy and can be made ahead of time.

Baked zucchini gratin in a black dish with a wooden spoon

Holiday meals are all about the side dishes for me! You can have so much fun with them and get really inventive! This zucchini gratin is everything a side dish should be – comforting, cheesy and packed full of flavor. This has to make an appearance on your table this year!

How To Make This Zucchini Au Gratin Recipe (Cheesy Zucchini Tian)

It looks like a lot of instructions, but this dish only takes 20 minutes to prep!

  • Spray a large (8-10 casserole dish with nonstick cooking spray.
  • Heat oven to 400°F and position oven rack to upper third position.

TO PREP THE ZUCCHINI FOR THE GRATIN:

  • Cut off the stem and tip from each zucchini. Gently scrub the zucchini and peel, if desired (important if using larger, tougher zucchini). *See note.
  • If available, use a food processor to grate the zucchini. If a food processor isn’t available, rub the zucchini against the coarse side of a grater. Place the grated zucchini in a large colander set over a large bowl. Sprinkle 1-teaspoon kosher salt over the zucchini and toss together until mixed thoroughly. Allow the squash to drain at least 10 minutes (or even overnight (covered). Line a large baking sheet with 3 layers of paper towels. Remove the colander from the bowl and squeeze the grated zucchini, one handful at-a-time, over the bowl with the reserved zucchini juice. Place the squeezed zucchini on the prepared baking sheet and repeat until excess juice has been drained from all the zucchini. Cover the zucchini with 2 layers of paper towels and press down; set the zucchini aside until ready to cook.
  • While the zucchini rests, cook the rice according to package directions EXCEPT cook the rice 5 minutes less than directed. Remove the rice from the heat and stir.
  • While the rice cooks, heat a large skillet over medium-low heat and add 3 tablespoons oil. When the oil is hot, add the diced onion and cook 8-10 minutes or until tender, translucent and beginning to brown lightly.
  • Add the minced garlic and, while stirring, cook an additional 30 seconds.
  • Add the dried zucchini and mix well. Cook 5-6 minutes or until the zucchini is almost tender.
  • Sprinkle the zucchini with the flour and mix well. Cook (and sti2 more minutes. Remove from the heat.
  • Heat the milk and 1 cup reserved zucchini juice in the microwave (or stovetojust until warm. Add the milk/juice to the zucchini mixture and stir until incorporated.
  • Set the pan over medium-low heat and add the par-cooked rice. Stir and cook about 5 minutes or until most of the excess liquid has reduced. Watch closely so it doesn’t scorch.
  • Remove from the heat and add ¾ cup grated Parmesan cheese. Stir well and season to taste with kosher salt & freshly ground black pepper, if needed.
  • Transfer zucchini/rice mixture to prepared dish, sprinkle evenly with reserved ¼ cup grated Parmesan and drizzle with olive oil.
  • Bake 30-40 minutes at 400°F or until bubbly throughout and top is golden brown. (If the casserole looks heated through and bubbly, but the top is still somewhat pale, set the oven to broil and cook another 2-3 minutes. Watch very closely until the zucchini gratin is golden brown and gorgeous on top.
  • Enjoy!

Close up of zucchini gratin on a wooden spoon

Close up of the rice in the dish

What To Serve With Zucchini Gratin?

This heart and comforting side dish is great to serve with all of your favorite holiday meals. I like to serve it straight in the dish to the table so everyone can help themselves. Serve it up with:

What Is A Tian?

This zucchini gratin is cooked in a tian, an earthenware baking dish that is used to cook and serve. If you don’t have an authentic French tian, you can use an ovenproof casserole dish or oven safe glass dish.

Zucchini gratin in a black baking dish with pieces served out of it

A cheesy baked side dish with rice

Is Zucchini Gratin Healthy?

Let’s be honest, the holidays aren’t really the time to be thinking about being healthy ha ha! This dish however, is a great way to get some extra veggies into your meal and I like to serve up a veggie gratin rather than a potato one. One generous serving is under 300 calories and you are getting a good amount of vitamins and minerals from those yummy zucchini.

Top Tips To Make Zucchini Gratin

  • Be sure to grease the dish before adding the ingredients for easy removal.
  • You can build the dish ahead of time and then keep it covered in the fridge until you are ready to cook it. Alternatively, you can cook it ahead of time and reheat it in the oven when you are ready to serve.
  • Really squeeze the liquid out of your zucchini so you don’t have a runny gratin.

Zucchini gratin garnished with fresh herbs

Be Sure To Check Out These Other Delicious Zucchini Recipes!

Recipe Card

Zucchini Au Gratin Recipe

4.91 from 10 votes
Prep: 20 minutes
Cook: 1 hour
Total: 1 hour 20 minutes
Servings: 8 people
Author: Becky Hardin
zucchini gratin in pan with wooden spoon
This delicious Zucchini Au Gratin Recipe is a great rice based side dish that's perfect to serve throughout the holidays.  This amazing zucchini casserole is deliciously cheesy and can be made ahead of time.
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Ingredients 

  • 2-2½ pounds zucchini yellow squash or a blend of both
  • 1 cup uncooked long-grain white rice NOT Minute Rice
  • 1 cup diced onions
  • 3 tablespoons olive oil
  • 2 large cloves garlic minced
  • 3 tablespoons flour
  • cups whole milk
  • 1 cup reserved zucchini juice
  • 1 cup grated Parmesan cheese divided
  • Kosher salt and freshly ground black pepper to taste
  • 2 tablespoons olive oil

Instructions 

  • Spray a large (8-10 cucasserole dish with nonstick cooking spray.
  • Heat oven to 400°F and position oven rack to upper third position.

To prep the zucchini:

  • Cut off the stem and tip from each zucchini. Gently scrub the zucchini and peel, if desired (important if using larger, tougher zucchini). *See note.
  • If available, use a food processor to grate the zucchini. If a food processor isn’t available, rub the zucchini against the coarse side of a grater. Place the grated zucchini in a large colander set over a large bowl. Sprinkle 1-teaspoon kosher salt over the zucchini and toss together until mixed thoroughly. Allow the squash to drain at least 10 minutes (or even overnight (covered). Line a large baking sheet with 3 layers of paper towels. Remove the colander from the bowl and squeeze the grated zucchini, one handful at-a-time, over the bowl with the reserved zucchini juice. Place the squeezed zucchini on the prepared baking sheet and repeat until excess juice has been drained from all the zucchini. Cover the zucchini with 2 layers of paper towels and press down; set the zucchini aside until ready to cook.
  • While the zucchini rests, cook the rice according to package directions EXCEPT cook the rice 5 minutes less than directed. Remove the rice from the heat and stir.
  • While the rice cooks, heat a large skillet over medium-low heat and add 3 tablespoons oil. When the oil is hot, add the diced onion and cook 8-10 minutes or until tender, translucent and beginning to brown lightly.
  • Add the minced garlic and, while stirring, cook an additional 30 seconds.
  • Add the dried zucchini and mix well. Cook 5-6 minutes or until the zucchini is almost tender.
  • Sprinkle the zucchini with the flour and mix well. Cook (and sti2 more minutes. Remove from the heat.
  • Heat the milk and 1 cup reserved zucchini juice in the microwave (or stovetojust until warm. Add the milk/juice to the zucchini mixture and stir until incorporated.
  • Set the pan over medium-low heat and add the par-cooked rice. Stir and cook about 5 minutes or until most of the excess liquid has reduced. Watch closely so it doesn’t scorch.
  • Remove from the heat and add ¾ cup grated Parmesan cheese. Stir well and season to taste with kosher salt & freshly ground black pepper, if needed.
  • Transfer zucchini/rice mixture to prepared dish, sprinkle evenly with reserved ¼ cup grated Parmesan and drizzle with olive oil.
  • Bake 30-40 minutes at 400°F or until bubbly throughout and top is golden brown. (If the casserole looks heated through and bubbly, but the top is still somewhat pale, set the oven to broil and cook another 2-3 minutes. Watch very closely until the zucchini is golden brown and gorgeous on top.
  • Enjoy!

Becky's Tips

Adapted slightly from Food52, Julia Child’s Zucchini Tian: https://food52.com/blog/4236-julia-child-s-zucchini-tian
*Note: If the zucchini is unpeeled, the color of the finished casserole will be much greener
Calories: 282kcalCarbohydrates: 29gProtein: 10gFat: 14gSaturated Fat: 4gCholesterol: 15mgSodium: 221mgPotassium: 492mgFiber: 2gSugar: 6gVitamin A: 453IUVitamin C: 27mgCalcium: 217mgIron: 1mg

Nutrition information is automatically calculated, so should only be used as an approximation.

Did you make this? Leave a comment!

Meet Becky Hardin

Becky Hardin is a wife and mother living in Saint Louis Missouri. She founded The Cookie Rookie in 2012 as a creative way to share recipes. Now, she is a trusted resource for easy cooking around the world, being featured in Taste of Home, The Kitchn, ABC’s Home and Family, and more. Here at The Cookie Rookie she is the editor in chief of all recipes and continues to enjoy sharing her passion for cooking for busy families. She has since founded two additional food blogs, Easy Chicken Recipes and Easy Dessert Recipes.

4.91 from 10 votes (4 ratings without comment)
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14 Comments
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Chandra
Chandra
September 6, 2022 9:01 pm

This was delicious! As you can see from the photo there wasn’t much left lol. I will definitely add this to my regular rotation. The only bad thing was that I cooked it for the full 40 minutes and it was still looking a little undercooked. I cooked it for an hour and it turned out great!5 stars

Last edited 2 years ago by Chandra
Samantha Marceau
September 7, 2022 9:11 am
Reply to  Chandra

Glad you enjoyed it!

Jackie
Jackie
September 6, 2019 8:39 pm

Hi
Did you use regular olive oil or extra-virgin olive oil.

Becky Hardin
Becky Hardin
September 13, 2019 3:01 pm
Reply to  Jackie

Regular, but you can use whatever you like!

Anna
Anna
September 4, 2019 12:18 pm

I ave so much zucchini to use up! This gratin looks fantastic!5 stars

Becky Hardin
Becky Hardin
September 6, 2019 9:43 am
Reply to  Anna

Well time to get started!

Beth Pierce
Beth Pierce
September 4, 2019 12:06 pm

What a savory dinner recipe! Definitely adding this to my dinner line up for the week! Yum!5 stars

Becky Hardin
Becky Hardin
September 6, 2019 9:45 am
Reply to  Beth Pierce

Thanks, Beth!

Stephanie
Stephanie
September 4, 2019 11:59 am

Such a great recipe! I love zucchini, so I’m all in on any new way to serve it.5 stars

Becky Hardin
Becky Hardin
September 6, 2019 9:49 am
Reply to  Stephanie

Yay! Thanks, Stephanie!

Tara
Tara
September 4, 2019 10:51 am

I can always use another zucchini recipe this time of year. This is a keeper!5 stars

Becky Hardin
Becky Hardin
September 6, 2019 9:45 am
Reply to  Tara

Thanks, Tara!

Toni
Toni
September 4, 2019 10:27 am

This is really impressive! My kids loved it!5 stars

Becky Hardin
Becky Hardin
September 6, 2019 9:49 am
Reply to  Toni

Thanks, Toni! Glad to hear they loved it!