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

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

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.

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:

Fish: Try Quick Broiled Salmon, Easy Pan Seared Salmon, Pesto Salmon, or Pan Fried Cod
Shrimp or Scallops: Opt for Creamy Shrimp Pasta, Easy Pesto Shrimp or Pan Seared Scallops
Chicken: Poultry goes especially well with roasted onions! They also work well as a Thanksgiving side dish or Christmas side.
Vegetarian/vegan main dishes: Try Eggplant Parmesan or Perfect Zucchini Lasagna

More onion recipes

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

Pickle them! Pickled onions add a briny tang to tacos, salads, and more! Try these 1-Hour Quick Pickled Onions.
Caramelize them! Cook them 1 hour until they’re sweet and tender with Perfect Caramelized Onions.
Saute them! In just 10 minutes, Simple Sauteed Onions are browned and tender.
Grill them! Try these smoky Grilled Onions, a fantastic summer side dish.
Make fried rice. Onions are perfect for flavoring aromatic fried rice. Use onions of all types in this Three Onion Fried Rice.

This roasted onions recipe is…

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