These Roasted Potatoes and Onions are the only roasted potato recipe you will ever need. Every bite is infused with fresh rosemary and whole grain mustard. They’re roasted for a long time so the potatoes get super crispy and the onions caramelize. The flavors are earthy, slightly sweet, and mustard-spicy-tangy, and your whole family will love them! Best of all, they’re easy enough to make on a casual weeknight, and fancy enough for a dinner party, Thanksgiving, or other holiday meal.
I think I could seriously eat a whole batch of these in one sitting. If they look familiar to you, they’re adapted from Ina Garten’s recipe. When my mother-in-law made them for dinner one night, I knew I needed to make a version for Bowl of Delicious. While Ina’s recipe is very good (I mean, she’s Ina Garten- of COURSE it’s good!), I made just a few tweaks to the recipe and process to highlight the roasted potatoes a bit more and ensure even roasting.
One of the things I always do when roasting vegetables is mix them in a large bowl with all the ingredients, THEN transfer to a baking sheet. So many recipes require spreading them out on a baking sheet, drizzling with oil, and adding the seasonings on top. I find that mixing in a bowl before ensures a much more even, thin coating on the vegetables and enables you to use less oil than you would when drizzling. When I add oil on top of veggies directly in the baking sheet, I find it pools up on the baking sheet, causing scary splattering in the oven.
If it looks like you are using a lot of onions, GOOD. It may seem like a lot at first, but don’t worry: they cook down substantially while roasting and they are potentially the most delicious part of this whole recipe, since they get wonderfully browned and caramelized in the oven.
Here are some other tips when making these roasted potatoes and onions.
- Cut the potatoes into pieces no bigger than a half an inch. This means more surface area to get deliciously browned and toasty tasting.
- Use PLENTY of salt. Potatoes are bland, and need a lot of it.
- Make sure you use a sturdy baking sheet (I swear by the classic Nordic Ware half baker’s sheet– it doesn’t buckle under high heat and nothing sticks to it!).
- Finally, make sure you stir the potatoes around only once- no more than that. You want to give the vegetables time to brown and their liquids to evaporate in between stirs. If you stir them too frequently, they will get recoated in the liquid, which will cause them to stick to the pan more easily and not crisp up quite as much.
Other easy potato side dish recipes:
- Everything Bagel Crispy Smashed Potatoes
- The BEST Twice-Baked Potatoes
- Nepalese Potato Salad
- Warm Potato Salad with Bacon and Arugula
Roasted Potatoes and Onions with Rosemary and Mustard
Equipment
Ingredients
- 1 yellow onion quartered and sliced to approximately 1/4-inch thick (see notes)
- 2.5 lbs red potatoes unpeeled, cut into approximately 1/2 inch cubes
- 3 tablespoons extra-virgin olive oil
- 1 tablespoon whole grain mustard
- 1 tablespoon chopped fresh rosemary
- kosher salt to taste
- black pepper to taste
Instructions
- Mix all ingredients in a large bowl (make sure you salt liberally!).
- Spread evenly on a sturdy rimmed baking sheet.
- Roast at 425 degrees for approximately 1 hour, stirring once halfway through, until potatoes are browned and onions crispy.
Notes
- It's important to not overcrowd the pan. Use two baking sheets if needed, or cut the recipe in half.
- The onions can cook a bit more than desired if sliced too thinly, and also I find if I'm using an electric oven (for some reason, gas never burned the onions for me, but when I switched to an electric one I had to keep a closer eye on it). If you're concerned about this or need to troubleshoot burnt onions, try slicing the onions a bit thicker or add them to the sheet pan a little ways into cooking the potatoes so they aren't in there the whole time.
Nutrition
Nutrition Information Disclaimer
The provided nutrition information is my best estimate and reflects one serving of the recipe (total servings indicated at top of recipe card). It does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. I use an automatic API to calculate this information. Feel free to calculate it yourself using one of these tools:
markhughw
About two thirds of the onions came out burnt. I was leery of slicing them thin at 425Iso I didn’t slice them too thin, about 1/4″ instead of 1/8 ” thick but still too thin. It was also too salty. If I were to make it again, I would slice them 1/2″ thick, but I will probably try a different recipe.
Elizabeth Lindemann
Oh no, that must have been frustrating. The onions do cook up quickly, and I realize I didn’t give a guideline in the recipe about how thick to slice them. Do you by any chance have an electric oven? I’ve used both and have found electric ovens to cook hotter than gas, which sometimes results in my onions being burned as well. I’m going to tweak the recipe card to address this issue. Hope that helps, for you or anyone else reading this!
markhughw
No, it is gas and I use an oven thermometer. I think I would quarter the onions and cut the onions 1/2 inch thick, and add them after the potatoes have cooked for 20 minutes, and cut the total to 45 minutes at 425. I saw another comment that said hers was done in 30 minutes.
Barbara Landis Ensor
Excellent recipe! Wouldn’t change a thing! Mine were done in about 30 minutes instead of 60, though. Might have been mine were smaller… Thanks for the great recipe that was a hit at Thanksgiving 2020. Barbie
Elizabeth Lindemann
So glad you liked them! You’re right- they probably cooked faster if they were cut smaller.
Carol M Klatt
After 40 minutes, onions were burnt, potatos ok. I’d probably lower the temperature next time.
Elizabeth Lindemann
Oh no! Sorry you had this frustrating experience. The onions do cook up to quite a crisp- mine turn almost black when I make this dish. I love how they taste, with the charred caramelization, but it’s possible your oven is just hotter than mine. I also cooked in the center of the oven- that can make a difference sometimes too. Maybe 400 degrees F instead of 425? Better luck next time!
Lyn
I followed this recipe but after 50 minutes it was burned to a crisp. I will try it again but cook for no more than 40-45 minutes.
Elizabeth Lindemann
Oh no! Every single oven I’ve ever used has been different in terms of temperature. It’s frustrating to never really know the exact time to bake things, and this has definitely happened to me before! I almost always check anything I’m roasting or baking every 20-30 minutes, or halfway through, depending on what it is, just to monitor the progress. This may also have to do with how big you cut the potatoes- if they are really small, they will cook faster. So sorry this happened- better luck next time!
Suzi
White onions OK to use?
Elizabeth
Yes, definitely!
Dr. J
These were amazing! Since my wife and I have been eating healthier, I’ve been frustrated in my attempts to make decent home fries (or whatever you call them), but these came out perfectly. And who would have thought mustard would work with potatoes? I didn’t even use the oil, just added a bit more mustard to make the rosemary and salt stick to the spuds. This will be our regular Saturday morning breakfast from now on.
Elizabeth
So happy you liked it! I agree- the mustard adds so much flavor!
Leslie
I made this tonight and it was very good. The onions are so delicious in the recipe – nice and sweet!
Elizabeth
Yay! Glad you liked it :)
lisa
First I have to say, there’s no such thing as too many onions! These look amazing Elizabeth. I’ve made many a roasted potato dish but nothing quite like this – the grainy mustard and rosemary are such a tempting combo. Cant wait to try this!
Maggie
I need to try out this recipe asap! I love PLENTY of crispy onion and mustard, so I’m sold! I’d probably add some bacon bits into this and call it a meal :)
Elizabeth
Excellent idea adding bacon!!