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Roasted onions are a healthy side dish that’s easy and full of flavor! Pair the tender, caramelized onions with balsamic and thyme.

Roasted onions
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Want a uniquely impressive healthy side dish? Try these Roasted Onions! We don’t often think of onions as a side dish (we more often think roasted broccoli or roasted potatoes). Roasting onions in a hot oven mellows their flavor until its deeply caramelized and sweet. Pair that with a hint of balsamic vinegar and herbaceous fresh thyme, and…just wow! Those simple flavors make an effortless side dish that goes with almost anything. Here are a few tricks for the best roasted onions.

Ingredients for roasted onions

The great thing about roasted onions is: all you need is time. (And thyme. Sorry, bad joke!) But really: there’s nothing hard about this recipe, and the ingredient list is very short. Here’s what you need for roasted onions:

  • Onions: you can use any variety! We used 2 red onions and 1 white onion. Each type of onion has a slightly different flavor. The hot oven transforms onions into a very mild flavor. Red onion has a beautiful purple color, so it makes for a stunning look.
  • Olive oil
  • Balsamic vinegar
  • Salt and pepper
  • Fresh thyme or other fresh herbs like chives or rosemary
Roasted onions

The best way to cut onions: French cut!

To make the very best roasted onions, it starts with your knife skills! The best way to slice onions for roasting is not into rings: it’s into elegant slivers. This type of cut is often called French cut, though it doesn’t really have a standardized name. Here’s what to do:

  • Slice off the ends, then cut in half: Once the ends are removed, stand the onion on its flat cut side and cut it down the center.
  • Remove the paper. With your fingers, remove the paper and outer layer of the onion.
  • Cut following the curve of the onion. Place the onion on its flat side then cut slices following the curve of the onion, from the tip to the root. Want to see? Go to minute 1:40 of this How to Cut an Onion video.

How to make roasted onions

You barely need a recipe for roasted onions! Once you’ve made it once, you can memorize it and repeat. All you need to remember is the oven temperature and how long to roast the onions. Interestingly, you can roast onions along with another vegetable at very high heat. But on their own, you’ll need to reduce the oven temperature! Jump to the full recipe or review the following:

  • Roast onions at 375 degrees Fahrenheit for 45 to 55 minutes. The timing will depend on the age of the onions and how thick you cut the slices.
  • Stir at 30 minutes. Give the onions a stir at 30 minutes, or they’ll get a little too blackened. Then you can add the fresh thyme.
  • How to season roasted onions? Drizzle on 2 tablespoons olive oil and 1 tablespoon balsamic vinegar for every 3 onions.
How to make roasted onions

Flavor variations!

Fresh thyme and balsamic are what we think is the best way to season roasted onions. But there are lots of ways to mix up the seasonings. Try the following:

  • Dijon mustard: Add a dollop of Dijon mustard with the olive oil
  • Fresh herbs: Use fresh rosemary or oregano instead of thyme
  • Honey or maple syrup: Add a hint more sweetness with a touch of honey or maple

What to pair with roasted onions

Roasted onions are a simple and elegant side dish to all sorts of main dish options. Here are a few ideas for what to serve with them:

Roasted onions

More onion recipes

Love onions? There are so many onion recipes for cooking this tasty root vegetable! What else to do with onions?

This roasted onions recipe is…

Vegetarian, vegan, plant-based, dairy-free and gluten-free

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Roasted onions

Easy Roasted Onions

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5 from 1 review

  • Author: Sonja Overhiser
  • Prep Time: 5 minutes
  • Cook Time: 45 minutes
  • Total Time: 50 minutes
  • Yield: 4 1x


Roasted onions are a healthy side dish that’s easy and full of flavor! Pair the tender, caramelized onions with balsamic and thyme.


  • 3 large onions (we used 2 red onion and 1 white onion)
  • 2 tablespoons olive oil
  • 1 tablespoon balsamic vinegar
  • ½ teaspoon kosher salt
  • Fresh ground pepper
  • 1 tablespoon chopped fresh thyme


  1. Preheat the oven to 375 degrees Fahrenheit.
  2. Cut the onions into wide strips (French cut). Toss them with olive oil, balsamic vinegar, kosher salt and pepper.
  3. Line a baking sheet with parchment paper. Place the onions on the baking sheet and roast 30 minutes. Remove from oven, stir and add the thyme.
  4. Continue cooking 15 to 25 or so minutes, until tender. Taste and add another ⅛ teaspoon salt, plus more as necessary. Serve immediately or store leftovers refrigerated for up to 4 days.
  • Category: Side Dish
  • Method: Roasted
  • Cuisine: American
  • Diet: Vegan

About the authors

Sonja & Alex

Hi, we’re Alex and Sonja Overhiser, married cookbook authors, food bloggers, and recipe developers. We founded A Couple Cooks to share fresh, seasonal recipes and the joy of cooking! Our recipes are made by two real people and work every time.

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  1. wanda cummings says:

    I am trying to figure out what to do with the garden onions. I dont have anywhere to store them, long term. After baking, can the onions be frozen

  2. Richard Becraft says:

    “Continue cooking 15 to 25 or so minutes, until tender.” Continue cooking in what?

    1. Alex Overhiser says:

      The oven.

  3. Kris Ramachandran says:

    Can I use the roasted / baked onions to make Onion Soup? What would be the additional steps? Thanks

    1. Alex Overhiser says:

      I think you would usually carmelize onions on the stovetop! We don’t have a recipe for onion soup, sorry.

  4. Rachel says:

    It says you need balsamic vinegar in the recipe but then in the directions doesn’t tell you went to add it.

    1. Sonja Overhiser says:

      This should be in Step 2 — the recipe is updated! Thank you!