🥕 Root Vegetable Gratin with Sweet Potatoes, Parsnips, and Beets

There is something about pulling a bubbling gratin from the oven that instantly makes dinner feel special.

This Root Vegetable Gratin with Sweet Potatoes, Parsnips, and Beets is one of those recipes I love making when the weather turns cool and I want something comforting on the table. It has all the cozy qualities of a classic gratin—creamy layers, tender vegetables, golden cheese, and that wonderful savory smell filling the kitchen—but the combination of root vegetables makes it feel a little more colorful and interesting.

I first made a version of this for a family dinner when I had a few beautiful root vegetables waiting in the kitchen. I wasn’t looking for anything complicated. I just wanted something that could sit beside a roast and make the whole meal feel a little more festive.

The result surprised me.

The sweet potatoes became soft and buttery, the parsnips developed a lovely earthy sweetness, and the beets added beautiful color and a subtle richness. Then the garlic, thyme, Parmesan, and Gruyère brought everything together.

Even the people who usually reach for the potatoes first went back for another serving.

That’s always a good sign.

And while it looks like the kind of dish that belongs on a holiday table, it’s simple enough for a Sunday dinner, too.

❤️ Why You’ll Love This Root Vegetable Gratin

• Beautiful and colorful enough for a holiday table.
• Creamy without needing a complicated sauce.
• Sweet potatoes, parsnips, and beets balance one another beautifully.
• Garlic and fresh thyme add savory depth.
• Parmesan adds flavor throughout the vegetables.
• Gruyère creates a golden, bubbling top.
• Most of the work is simply slicing and arranging the vegetables.
• It pairs beautifully with roasted chicken, beef, pork, or lamb.
• It can be assembled ahead of time.

Thin, evenly sliced root vegetables are particularly important in gratins because different vegetables can otherwise finish cooking at different rates. A mandoline makes this much easier, although a sharp knife works perfectly well.

🛒 Ingredients You’ll Need

For the Vegetables

• 2 medium sweet potatoes, peeled
• 3 medium parsnips, peeled and trimmed
• 2 medium beets, peeled
• 1 tablespoon unsalted butter, softened, for the baking dish
• ¾ cup heavy cream, divided
• ½ cup finely grated Parmesan cheese, divided
• 1 tablespoon fresh thyme leaves, finely chopped
• 2 cloves garlic, minced
• 1 teaspoon kosher salt, plus more to taste
• ½ teaspoon freshly ground black pepper

For the Golden Cheese Topping

• 1 cup shredded Gruyère cheese

Optional Garnish

• Fresh thyme leaves
• Flaky sea salt
• Freshly cracked black pepper

The combination of heavy cream, garlic, thyme, Parmesan, and Gruyère is particularly well suited to these vegetables; similar root-vegetable gratins use the same basic creamy-cheesy approach.

🔪 The Most Important Step: Slice Everything Thinly

Before you begin assembling, take your time with the vegetables.

You want the sweet potatoes, parsnips, and beets sliced into very thin, even rounds—about ⅛ inch thick.

A mandoline makes quick work of this, but please use the safety guard. If you’re using a knife, take your time and aim for consistent slices.

The more evenly everything is sliced, the more evenly the gratin will cook.

👩‍🍳 How to Make Root Vegetable Gratin

1. Preheat the Oven

Preheat your oven to 400°F (200°C).

Butter a 3-quart baking dish thoroughly.

I like using an oval or rectangular dish where the vegetables can fit snugly.

2. Prepare the Sweet Potatoes

Place the thinly sliced sweet potatoes in a bowl.

Add:

• ¼ cup heavy cream
• 2 tablespoons Parmesan
• 1 teaspoon fresh thyme
• A little salt
• A little black pepper

Gently toss until the slices are lightly coated.

3. Prepare the Parsnips

Place the sliced parsnips in a second bowl.

Add another:

• ¼ cup heavy cream
• 2 tablespoons Parmesan
• 1 teaspoon fresh thyme
• Salt
• Black pepper

Toss gently.

4. Prepare the Beets Separately

Place the beet slices in their own bowl.

Add:

• 2 tablespoons heavy cream
• 2 tablespoons Parmesan
• Remaining thyme
• Salt
• Pepper

Toss gently until coated.

Why keep the beets separate?

Because beets naturally release their gorgeous deep color as they cook.

Keeping them separate during preparation prevents everything from turning purple before you’ve even assembled the dish.

You’ll still get beautiful beet-colored edges once everything bakes together.

🧄 5. Prepare the Baking Dish

Spread the remaining ¼ cup heavy cream over the bottom of the buttered baking dish.

Scatter the minced garlic over the cream.

Add another small sprinkle of Parmesan.

This creates a flavorful base underneath the vegetables.

🥔 6. Arrange the Vegetables

Now comes the fun part.

Instead of simply dumping everything into the baking dish, arrange the vegetable slices in overlapping rows.

Start with:

Sweet potato → parsnip → beet → sweet potato → parsnip → beet

Continue until the dish is filled.

You can arrange the vegetables upright at a slight angle, packed closely together, or create traditional overlapping layers.

The upright method makes a particularly beautiful presentation because you can see the different colors across the top.

Don’t worry about perfection.

A rustic gratin is supposed to look homemade.

🧀 7. Add the Remaining Parmesan

Once all the vegetables are arranged, sprinkle the remaining Parmesan over the top.

Give everything one final light seasoning with salt and pepper.

Then cover the baking dish tightly with aluminum foil.

🔥 8. Bake Covered

Place the covered gratin in the oven.

Bake for approximately 30 minutes.

The covered baking time allows the vegetables to steam gently and soften without the top becoming too dark.

🧀 9. Add the Gruyère

Remove the foil carefully—the steam will be hot.

Sprinkle the Gruyère evenly over the top.

Return the uncovered dish to the oven.

Bake for another 20–25 minutes, or until:

• The vegetables are fork-tender.
• The cheese is bubbling.
• The top is golden brown.
• The edges are beautifully caramelized.

If your vegetables are thicker than ⅛ inch, they may need additional time.

A thin knife should slide easily through the center when they’re done.

🌿 10. Let It Rest

This is an easy step to overlook.

Take the gratin out of the oven and let it rest for about 10 minutes.

This gives the cream and melted cheese a chance to settle.

It also makes the gratin easier to serve without everything sliding apart.

Finish with fresh thyme and, if you like, a little flaky sea salt.

🍽️ What to Serve With Root Vegetable Gratin

This is a wonderfully versatile side dish.

For Sunday Dinner

Serve it with:

• Roast chicken
• Roast beef
• Pork tenderloin
• Herb-roasted pork
• Roast lamb
• Turkey

For a Holiday Table

It would be beautiful alongside:

• Turkey
• Glazed ham
• Prime rib
• Roast chicken
• Green beans
• Brussels sprouts
• Cranberry sauce
• Simple green salad

For a Vegetarian Meal

Make the gratin the star of the plate with:

• Arugula salad
• Roasted Brussels sprouts
• Sautéed greens
• Lentil salad
• Crusty bread

The combination is rich enough to work as a vegetarian main course with a fresh salad on the side.

💡 My Best Tips for Perfect Gratin

Slice the vegetables evenly

This is probably the most important tip.

If your sweet potatoes are paper-thin but your parsnips are twice as thick, they’ll finish cooking at different times.

Don’t skip the foil

The covered portion of baking helps the root vegetables become tender before the cheese gets too brown.

Keep the beets separate

This isn’t essential, but it makes preparation much less messy and helps preserve those pretty color distinctions.

Pack the vegetables closely

Especially if you’re arranging them upright.

The slices support one another and create those beautiful layers.

Don’t drown the vegetables in cream

A gratin should be creamy, but you don’t want the vegetables swimming in liquid.

The cream should coat the vegetables and collect underneath them.

Grate your own cheese

Freshly grated Gruyère melts beautifully and gives you a smoother, more luxurious topping.

Let it rest

Ten minutes makes a noticeable difference when serving.

🧀 Choosing the Right Cheese

Gruyère

My first choice.

It’s nutty, savory, and melts beautifully.

Parmesan

Excellent for adding salty, concentrated flavor throughout the layers.

Comté

A wonderful substitute for Gruyère.

It has a similarly nutty, sophisticated flavor.

Sharp Cheddar

If that’s what you have, go for it.

The flavor will be bolder and more familiar.

Emmental

A milder option that melts beautifully and works particularly well with root vegetables.

🌿 Easy Variations

Garlic Rosemary Gratin

Replace half the thyme with fresh rosemary.

Rosemary gives the dish a stronger, woodsy flavor that works beautifully with parsnips.

Caramelized Onion Gratin

Add thinly sliced caramelized onions between the vegetable layers.

The sweetness is fantastic with the beets and sweet potatoes.

Extra-Cheesy Gratin

Add a little shredded Gruyère between some of the vegetable layers as well as on top.

Don’t go overboard—you still want the vegetables to shine.

Nutty Holiday Gratin

Sprinkle ¼ cup toasted chopped walnuts or pecans over the finished gratin.

Add them after baking so they stay crunchy.

Dairy-Free Version

Use a dairy-free cooking cream or unsweetened coconut cream and replace the cheese with a suitable dairy-free alternative.

The flavor will be slightly different, but the vegetables still work beautifully with garlic and herbs.

🍠 Can I Add Other Root Vegetables?

Absolutely.

This recipe is flexible.

You can replace some of the vegetables with:

• Yukon Gold potatoes
• Carrots
• Rutabaga
• Turnips
• Celery root

A mixed-root gratin is a great way to use whatever looks best at the market.

Root-vegetable gratins commonly use combinations of potatoes, beets, fennel, parsnips, and other roots, so there is plenty of room to customize the vegetable mixture.

🕒 Can I Make This Ahead?

Yes.

For a dinner party or holiday meal, you can assemble the gratin several hours ahead.

Cover it tightly and refrigerate.

Take it out about 30 minutes before baking so the dish isn’t going straight from a cold refrigerator into a hot oven.

Then bake according to the recipe, allowing a little extra time if necessary.

For the freshest, crispiest cheese topping, add the Gruyère shortly before the uncovered baking stage.

🧊 How to Store Leftovers

Let the gratin cool and transfer leftovers to an airtight container.

Refrigerate for up to 3 days.

Similar root-vegetable gratin recipes recommend refrigeration for around three days and reheating gently to protect the topping.

To Reheat

Place the leftovers in a baking dish and cover loosely with foil.

Reheat at 350°F until warmed through.

Remove the foil for the final few minutes if you’d like to crisp the cheese again.

Individual portions can also be reheated in the microwave, although the oven gives you the best texture.

❓ Frequently Asked Questions

Do I have to use a mandoline?

No.

A sharp chef’s knife works perfectly. Just try to keep the slices consistently thin.

Can I use pre-shredded cheese?

You can, but freshly grated Gruyère generally melts more smoothly.

Will the beets turn everything pink?

Some color transfer is normal, especially around the beet slices.

Keeping the beets separate during preparation helps keep the other vegetables more distinct.

Why is my gratin watery?

The vegetables naturally release moisture as they cook.

If the gratin seems watery, leave it uncovered for an additional 5–10 minutes in the oven so some of the excess moisture can evaporate.

Why are my vegetables still firm?

The slices may be too thick, or the gratin may simply need more time.

Cover it again with foil and continue baking until a knife passes easily through the center.

Can I use milk instead of heavy cream?

You can, but the gratin will be less rich and may be less creamy.

Heavy cream gives the dish its classic luxurious texture.

Can I make this without cheese?

Yes.

You can make a creamy root vegetable gratin without cheese, although the finished dish won’t have the same golden savory crust.

Is this gluten-free?

The basic recipe contains no wheat-based ingredients, making it naturally gluten-free as written. Always check packaged ingredients such as cheese if you need to avoid gluten strictly.

Can I freeze the gratin?

You can, but I prefer refrigeration.

Freezing and thawing can make the vegetables softer and the creamy sauce less smooth.

For the best texture, make it fresh or refrigerate leftovers.

📝 Recipe at a Glance

Recipe: Root Vegetable Gratin with Sweet Potatoes, Parsnips, and Beets
Prep Time: 25 minutes
Cook Time: 50–55 minutes
Rest Time: 10 minutes
Total Time: About 1 hour 30 minutes
Servings: 6–8
Category: Side Dish
Cuisine: American-inspired
Best For: Sunday dinners, Thanksgiving, Christmas, and cozy family meals

🥕 Root Vegetable Gratin with Sweet Potatoes, Parsnips, and Beets

Ingredients

Vegetables

• 2 medium sweet potatoes, peeled and thinly sliced
• 3 medium parsnips, peeled and thinly sliced
• 2 medium beets, peeled and thinly sliced
• 1 tablespoon unsalted butter, for the dish
• ¾ cup heavy cream, divided
• ½ cup finely grated Parmesan, divided
• 1 tablespoon fresh thyme leaves, chopped
• 2 cloves garlic, minced
• 1 teaspoon kosher salt
• ½ teaspoon black pepper

Topping

• 1 cup shredded Gruyère

Garnish

• Fresh thyme
• Flaky sea salt, optional

Instructions

1. Preheat oven to 400°F (200°C).
2. Butter a 3-quart baking dish.
3. Slice sweet potatoes, parsnips, and beets into approximately ⅛-inch rounds.
4. Toss sweet potatoes with ¼ cup cream, 2 tablespoons Parmesan, 1 teaspoon thyme, salt, and pepper.
5. Toss parsnips with another ¼ cup cream, 2 tablespoons Parmesan, 1 teaspoon thyme, salt, and pepper.
6. Toss beets with 2 tablespoons cream, 2 tablespoons Parmesan, remaining thyme, salt, and pepper.
7. Spread the remaining ¼ cup cream across the bottom of the baking dish.
8. Scatter the minced garlic and a little Parmesan over the cream.
9. Arrange the vegetables in overlapping or slightly upright alternating rows.
10. Sprinkle the remaining Parmesan over the vegetables.
11. Cover tightly with foil.
12. Bake for 30 minutes.
13. Remove the foil and sprinkle evenly with Gruyère.
14. Bake uncovered for 20–25 minutes, until the vegetables are tender and the cheese is golden and bubbling.
15. Let rest for 10 minutes.
16. Garnish with fresh thyme and flaky salt.
17. Serve warm.

❤️ Final Thoughts

I think this is one of those recipes that proves a vegetable side dish doesn’t have to be an afterthought.

Look at that platter when it comes out of the oven—golden cheese on top, creamy edges, and those beautiful ribbons of orange, ivory, and ruby red underneath.

It feels festive.

But underneath all that beauty, it’s still just simple root vegetables, cream, garlic, herbs, and cheese.

That’s what I love about it.

It’s the kind of dish I would happily make for a holiday dinner, but I also wouldn’t hesitate to make it on a quiet Sunday when the family is gathered around the table.

And if there happens to be a little bit left the next day?

Even better.

The flavors settle together overnight, and reheated slices make an incredibly comforting lunch.

Sometimes the side dish ends up being the thing everyone remembers.

I have a feeling this gratin will be one of those recipes.