These Roasted Sweet Potatoes and Onions come out tender and creamy in the center with beautifully browned edges, while the onions soften and get deeply browned in spots. Fresh rosemary keeps the whole pan savory and makes this an easy side dish for everything from weeknight dinners to holiday meals.
I've made this recipe for years, but when I went back and retested it, I realized I was making it more complicated than it needed to be. The best version was also the simplest: a preheated sheet pan, a 450°F oven, no cornstarch and rosemary added near the end.
What Makes This Different
- The pan preheats with the oven. It doesn't add any extra time, but the vegetables start sizzling the second they hit the hot metal, which gives the browning a head start.
- There's no cornstarch. I tested it hoping it would make the sweet potatoes noticeably crispier, but I honestly couldn't tell enough of a difference to justify the extra step. These aren't French-fry crispy; the goal is browned edges with soft, creamy centers.
- The potatoes and onions roast together. No separate pans or staggered start times. Some of the onion layers will naturally separate as they roast, and that's completely fine.
- The rosemary goes in near the end. Finely chopped rosemary can dry out, darken and turn bitter if it roasts at 450°F for the full 30 minutes. Adding it for just the last 8 minutes gives it enough time to flavor the vegetables without overcooking.
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Ingredients
- Sweet potatoes: Orange-fleshed sweet potatoes work best here. Try to cut them into fairly even pieces so they roast at the same rate. Bigger chunks take longer to become tender.
- Sweet onion: Vidalia, Walla Walla or another sweet onion works especially well here, but yellow or white onion is fine, too. Don't worry if the layers separate when you toss them with oil. That's normal and actually gives you a mix of softer pieces and darker browned edges.
- Oil: Use a neutral, high-heat oil such as avocado, vegetable or canola. Since these roast at 450°F, I prefer an oil that handles high heat well without adding much flavor of its own.
- Kosher salt and black pepper: Season before roasting, then taste again when the pan comes out of the oven. Don't be shy with the salt here. It helps balance the natural sweetness of the potatoes and onions.
- Fresh rosemary: Its piney, savory flavor balances the sweetness of the potatoes and onions. I add it near the end so it has time to flavor the vegetables without drying out or getting bitter in the high heat.
How to make Roasted Sweet Potatoes and Onions
Season the Vegetables
Place the sweet potatoes and onion in a large bowl. Add the oil, salt and pepper and toss until everything is evenly coated.
Roast
Add the vegetables to the preheated pan in a single layer. Roast for 15 minutes, stir, then roast again for 7 minutes.
Sprinkle the rosemary over the vegetables, stir again and roast for another 8 minutes, or until the sweet potatoes are tender with browned edges and the onions are soft and browned in spots.
Before You Make This
Give everything some room. One and a half pounds of sweet potatoes plus one medium onion fits comfortably on a large sheet pan. Spread everything into a single layer so the vegetables roast instead of steam.
Leave the pan alone for the first 15 minutes. This gives the vegetables uninterrupted contact with the hot sheet pan so the first side has time to brown before you stir.
Don't chase perfect onion wedges. Onion layers naturally separate when they're cut, tossed with oil and stirred. Some pieces will stay chunky and others won't. That's normal.
Add the rosemary late. Finely chopped rosemary doesn't need the full roasting time. Stirring it in for the last 8 minutes keeps the flavor noticeable without over-roasting it.
What to Serve with Roasted Sweet Potatoes & Onions
These are simple enough for a weekday dinner but work just as well on a holiday table.
For an everyday meal, I like them with these crispy baked chicken thighs. The salty, savory chicken is a nice contrast to the sweetness of the potatoes and onions.
Leftovers are also good tossed into a salad or turned into a breakfast hash with sautéed mushrooms, a fried egg and a little Parmesan.
FAQs
Not in the same way a roasted russet potato or french fry does. Sweet potatoes naturally roast up softer, so the better goal is browned edges with a tender, creamy center.
I tested adding cornstarch to this recipe specifically to see if it would make them noticeably crispier. For me, it didn't make enough of a difference to be worth the extra step.
No. When the potatoes are cut into ¾-inch cubes, they cook all the way through during the 30-minute roast at 450°F. There's no need to add a boiling step.
Make Ahead and Storage
Prep ahead: You can peel and cube the sweet potatoes in advance, but keep them completely submerged in cold water in the refrigerator so they don't discolor. They can be stored this way for up to 3 days, although I'd use them within a day or two for the best texture. Drain well and DRY THEM THOROUGHLY before tossing with oil; the drier the surface, the better they'll brown in the oven.
Leftovers: Store leftover roasted sweet potatoes and onions in an airtight container in the refrigerator.
Reheating: For the best texture, reheat them in a 400°F oven until hot, or in an air fryer at 375°F for 3-5 minutes, shaking the basket halfway through.
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Recipe
Roasted Sweet Potatoes and Onions with Rosemary
Ingredients
- 1½ pounds sweet potatoes, peeled and cut into ¾-inch chunks
- 1 medium sweet onion, cut into wedges or chunks
- 2 tablespoons avocado, vegetable or canola oil
- ¾ Kosher salt, plus more to taste
- ½ ground black pepper
- 2 teaspoons finely chopped fresh rosemary
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Instructions
- Preheat oven and pan. Place a large rimmed sheet pan in the oven and preheat to 450℉.
- Season vegetables. Place the sweet potatoes and onion in a large bowl. Drizzle with oil and sprinkle with salt and pepper. Toss until evenly coated.1½ pounds sweet potatoes, , 1 medium sweet onion, , 2 tablespoons avocado, vegetable or canola oil, ¾ Kosher salt, , ½ ground black pepper
- Roast for 15 minutes. Carefully remove the hot sheet pan from the oven. Spread the vegetables over the pan in a single layer. Return to the oven and roast, undisturbed, for 15 minutes.
- Stir and continue roasting. Remove the pan from the oven and stir the vegetables. Return to the oven and roast for 7 minutes.
- Add rosemary. Sprinkle the rosemary over the vegetables and stir to distribute evenly.2 teaspoons finely chopped fresh rosemary
- Finish roasting. Return the pan to the oven and roast for another 8 minutes or until the sweet potatoes are tender in the center with browned edges and the onions are soft and browned in spots.
- Season and serve. Taste and add more salt if needed. Serve warm.
Notes
- Be careful when adding the vegetables to the preheated sheet pan; it will be very hot.
- Keep the vegetables in a single layer so they have room to brown.
- Don't worry if some of the onion layers separate during roasting.
- Larger sweet potato cubes may need a few extra minutes.
- Yellow or white onion can be substituted for sweet onion.
- Reheat leftovers in a 400°F oven or at 375°F in an air fryer until hot.
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Nutrition
Nutrition info not guaranteed to be accurate.
Veronica says
Made these today, oh my so amazing! Big hit at Thanksgiving dinner! Perfection! So so good! Thank you for such a great recipe!
I'm so glad they helped make your Thanksgiving meal a hit. Thanks for letting us know!
Amy @ A Healthy Life For Me says
I am always looking for ways to serve up sweet potatoes. Love them.
Sweet potatoes are a crowd pleaser around here, and these go quickly whenever I make them for dinner.
Debbie says
Can you make this the day before and reheat - say for Thanksgiving? Also, does it travel well if you need to take your dish to your relatives? Thanks!
Naturally they will taste best the day they are made, but reheating them on a hot sheet pan in the oven is always an option. I would suggest reheating them wherever you go for your meal rather than taking them preheated as they will steam in a closed container and become softer. Hope that helps!
Pam Lutz says
I love rosemary, but never considered using it with sweet potatoes. I never considered combining onions with sweet potatoes either. This was absolutely delicious and I will definitely make it again. After posting a photo of my meal, I was asked for the recipe. Since I shared it, I've seen many of my friends also sharing recipes from your blog. All look wonderful and I can't wait to try some others.
Thanks for the comment, Pam. So glad you're finding some fun new recipes here!
paleo moxie says
Not always the biggest fan of rosemary but I loved this and will absolutely make it again! Perfect.