If you need a vegetable side dish that can hold its own next to the turkey, ham, or prime rib, this zucchini gratin deserves a place on your table. Tender zucchini and sweet onions are baked in a creamy sauce beneath a golden layer of Gruyère cheese and buttery breadcrumbs. It feels special enough for Thanksgiving or Christmas dinner, but it is still simple enough to make for Sunday supper.
This recipe comes from Ina Garten, which means it is elegant without being unnecessarily complicated. I made it as part of my Cooking With the Experts series alongside Ina’s Crispy Mustard Roasted Chicken. The two recipes make a beautiful dinner together, but this easy zucchini gratin could be served with just about any roasted meat.
Unlike a heavier potato gratin, zucchini keeps this side dish a little lighter while the cream sauce, Gruyère, and crisp breadcrumb topping still give you that rich holiday comfort-food feeling. It is a wonderful option when you want something green on the table but nobody is particularly excited about plain steamed vegetables.
Why You’ll Love This Zucchini Gratin
There are plenty of reasons this Ina Garten zucchini gratin works so well for both family dinners and holiday entertaining:
- It turns an everyday vegetable into a special side dish.
- The creamy sauce is rich without completely overpowering the zucchini.
- Gruyère cheese gives the gratin a nutty, savory flavor.
- The breadcrumb topping becomes golden and crisp in the oven.
- It pairs well with chicken, turkey, ham, beef, or pork.
- Most of the ingredients are easy to find at the grocery store.
- It looks beautiful served directly from the baking dish.
This is also a good recipe for anyone trying to add more variety to a traditional Thanksgiving or Christmas menu. We all love mashed potatoes and casseroles, but it is nice to have a vegetable side dish that still feels worthy of the holiday table.
What Is a Gratin?
A gratin is a baked dish finished with a browned crust, usually made from cheese, breadcrumbs, or a combination of the two. Potato gratin may be the version most people recognize, but the same technique works beautifully with zucchini.
In this zucchini gratin recipe, sliced zucchini and onions are combined with a creamy sauce and then topped with Gruyère and breadcrumbs. As the dish bakes, the vegetables become tender, the sauce thickens, and the topping turns golden brown.
For the best presentation, bake and serve the gratin in a pretty oven-safe casserole dish. I like using a shallow dish because it gives you more surface area for that cheesy breadcrumb topping.
Favorite shallow ceramic baking dish or gratin dish
Ingredients for Zucchini Gratin
The full measurements and instructions are included in the recipe card below, but here are the primary ingredients you will need:
Zucchini
Fresh zucchini is the star of this dish. Choose zucchini that feel firm and heavy for their size, without soft spots or wrinkled skin. Medium zucchini are usually easier to slice and have fewer large seeds than oversized ones.
Yellow Onion
Thinly sliced yellow onion adds sweetness and savory flavor. Cooking the onion before baking the gratin helps soften it and brings out its natural sweetness.
Butter
Butter is used to cook the vegetables and create the base of the creamy sauce. It also adds richness to the finished gratin.
Flour
A small amount of all-purpose flour thickens the sauce so it coats the zucchini instead of pooling in the bottom of the baking dish.
Milk
Warm milk creates a smooth, creamy sauce. Warming the milk before adding it to the pan helps it blend more easily with the flour and butter.
Small saucepan for warming milk
Nutmeg
Nutmeg is a classic addition to creamy sauces. You only need a small amount, but it adds warmth and depth without making the dish taste sweet.
Gruyère Cheese
Gruyère melts beautifully and has a nutty flavor that makes this zucchini gratin taste extra special. For the best texture, grate the cheese from a block instead of using pre-shredded cheese.
Breadcrumbs
Breadcrumbs create the crisp, golden topping. Combined with the Gruyère, they give the gratin a little texture against the tender zucchini and creamy sauce.
How to Make Zucchini Gratin
Begin by slicing the zucchini and onion. Try to keep the slices fairly even so the vegetables cook at the same rate. A sharp chef’s knife works perfectly, but a mandoline slicer can make the job especially quick.
Melt the butter in a large skillet and cook the onions over low heat until they are tender. Add the zucchini and continue cooking until it begins to soften. You want the vegetables tender, but not completely cooked through, since they will continue cooking in the oven.
Season the vegetables, then stir in the flour. Allow the flour to cook briefly before adding the warm milk. This removes the raw flour taste and helps create a smooth sauce.
Cook the mixture until the sauce begins to thicken. Transfer everything to a prepared baking dish, then cover the top with breadcrumbs and grated Gruyère cheese.
Bake until the zucchini is tender, the sauce is bubbling, and the top is golden brown. Let the gratin rest for a few minutes before serving. This gives the sauce a chance to settle and makes the dish easier to spoon onto plates.
How to Keep Zucchini Gratin From Becoming Watery
Zucchini naturally contains quite a bit of water, so there are a few things you can do to keep your gratin creamy instead of watery.
First, do not skip cooking the zucchini in the skillet. This begins releasing some of its moisture before it goes into the baking dish.
Second, avoid covering the gratin while it bakes. Baking it uncovered allows extra moisture to evaporate and helps the topping become crisp and golden.
Finally, let the finished zucchini gratin rest for about 10 minutes before serving. It will be extremely hot when it comes out of the oven, and the short resting time allows the creamy sauce to thicken slightly.
The Perfect Thanksgiving Vegetable Side Dish
Thanksgiving tables tend to be filled with rich, beige food, and I say that with great affection. This zucchini gratin adds a little green to the table without feeling like the obligatory healthy vegetable nobody wants.
The creamy Gruyère sauce and golden breadcrumb topping fit right in beside turkey, dressing, mashed potatoes, and all the casseroles. It is especially helpful if you are looking for a Thanksgiving side dish that feels traditional but is not the same recipe everyone else is bringing.
Serve this zucchini gratin alongside:
- Roasted turkey
- Glazed ham
- Beef tenderloin
- Prime rib
- Roasted chicken
- Pork tenderloin
Serve It for Christmas Dinner
This creamy zucchini casserole is just as fitting for Christmas as it is for Thanksgiving. It pairs especially well with glazed ham, roasted beef, or pork tenderloin and looks beautiful in a decorative baking dish on a Christmas buffet.
If your family serves a rich main course for Christmas dinner, zucchini gratin gives everyone the creamy, cheesy flavors they want without adding another potato-based side. The golden topping also makes it feel much more celebratory than a bowl of plain vegetables.
Add it to a Christmas dinner menu with Ina Garten’s Crispy Mustard Roasted Chicken for a smaller gathering, or serve it beside beef bourguignon for the ultimate comfort-food meal.
Can Zucchini Gratin Be Made Ahead?
Zucchini gratin is best when freshly baked because that is when the breadcrumb topping is at its crispiest. However, you can complete some of the preparation ahead of time.
Slice the zucchini and onions earlier in the day and store them separately in the refrigerator. You can also grate the Gruyère and prepare the breadcrumb topping in advance.
If you want to assemble the entire gratin ahead of time, prepare it through the topping step, cover it, and refrigerate it for a few hours. Remove the baking dish from the refrigerator while the oven preheats. You may need to add a few extra minutes to the baking time since the dish will be cold.
For holiday meals, I prefer preparing the vegetables, cheese, and baking dish in advance, then assembling and baking the gratin closer to serving time. This helps preserve the best texture.
Storing and Reheating Leftovers
Store leftover zucchini gratin in an airtight container in the refrigerator for up to three days.
To reheat a larger portion, place it in an oven-safe dish and warm it in a 350°F oven until heated through. The oven will do a better job of reviving the breadcrumb topping than the microwave.
Individual servings can be reheated in the microwave, although the topping will be softer. If you have an air fryer or countertop oven, that is another good option for reheating a small portion.
What to Serve With Zucchini Gratin
Although this is a beautiful holiday side dish, there is no reason to save it only for Thanksgiving and Christmas. It is also delicious with an easy chicken dinner, pork chops, steak, or even a simple rotisserie chicken.
Try serving it with:
- Ina Garten’s Crispy Mustard Roasted Chicken
- Sheet Pan Sausage and Peppers with Gnocchi
- Beef Bourguignon over Mashed Potatoes
- Creamy Tomato Chicken
- One Pan Salmon with Dates and Asparagus
For an easy family dinner, serve the gratin with roasted chicken and a simple green salad. For a holiday meal, add it to the table with your favorite meat, potatoes, rolls, and one fresh or acidic side to balance the richness.
More Recipes From Cooking With the Experts
This zucchini gratin is part of my Cooking With the Experts series, where I make recipes from the people who know food best. I love seeing which techniques are worth borrowing, which recipes deserve a permanent place in my kitchen, and how these famous dishes work in a real family home.
If you enjoyed this Ina Garten zucchini gratin, try another recipe from the series:
A Holiday Side Dish Worth Saving
This zucchini gratin proves that vegetable side dishes do not have to be plain or forgettable. The zucchini becomes tender, the onions add sweetness, and the creamy Gruyère sauce brings everything together beneath a crisp breadcrumb topping.
It is easy enough for a family dinner, elegant enough for company, and right at home on a Thanksgiving or Christmas table. If you are looking for a new holiday vegetable side dish that will actually have people reaching for seconds, save this one.
Grab a plate!
Ina's Zucchini Gratin
Equipment
- Large saute pan with lid
- 9x9 inch baking dish
- sharp knife or mandoline
- cheese grater
Ingredients
- 6 tablespoon unsalted butter, divided, plus more for greasing the baking dish
- 1 lb yellow onions, halved and sliced thin
- 2 lbs zucchini, sliced ¼ inch thick
- 2 teaspoon kosher salt
- 1 teaspoon black pepper
- ¼ teaspoon freshly ground nutmeg (optional)
- 2 tablespoon all purpose flour
- 1 cup hot milk
- ¾ cup fresh breadcrumbs (I used panko)
- ¾ cup grated gruyere cheese
Instructions
- Preheat the oven to 400°F. Butter an 9x9-inch baking dish.
- Melt 5 tablespoons of butter in a large sauté pan over low heat. Add the onions and cook for approximately 20 minutes, or until tender but not browned.
- Add the sliced zucchini to the pan. Cover and cook for approximately 10 minutes, stirring occasionally, until the zucchini is tender.
- Add the salt, black pepper, and nutmeg. Cook uncovered for another 5 minutes.
- Sprinkle the flour over the vegetables and stir to coat. Cook over low heat for 2 to 3 minutes.
- Slowly pour in the hot milk while stirring. Cook for a few minutes, until the sauce thickens slightly.
- Transfer the zucchini mixture to the prepared baking dish.
- Combine the breadcrumbs and Gruyère cheese in a small bowl. Sprinkle the mixture evenly over the zucchini, then dot the top with the remaining tablespoon of butter.
- Bake for approximately 20 minutes, until the gratin is bubbling and the topping is golden brown. Serve warm.
Notes
- Slice the zucchini evenly so it cooks at the same rate.
- Keep the heat low while cooking the onions. They should become soft and sweet without browning.
- Freshly grated Gruyère melts better than packaged shredded cheese.
- If the topping needs additional color, place the gratin under the broiler for 1 to 2 minutes, watching it carefully.
- This recipe is adapted from Ina Garten’s zucchini gratin in Barefoot in Paris and was featured in Episode 5 of my Cooking With the Experts series.
Key Takeaways
- Zucchini gratin transforms simple vegetables into an elegant side dish, perfect for holidays and family dinners.
- The creamy Gruyère sauce and crispy breadcrumb topping enhance the dish while keeping it light and flavorful.
- This recipe uses easily accessible ingredients and pairs well with various main courses, making it versatile.
- You can prepare some elements in advance, but fresh baking yields the best texture and taste.
- Zucchini gratin fits beautifully on both Thanksgiving and Christmas tables, providing a festive touch.
