Roasted onions make for an easy winter side dish (or condiment?). Dress them up with herbs and garlic or keep them simple with salt and pepper. You just need a sheet pan and 20 minutes to caramelize red onions in the oven. Try them for meal prep!

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I use this roasted red onion recipe as a standalone side dish but you can try this recipe for topping a roasted veggie sandwich, or really any sandwich! My favorite fancy burgers or my blackened chicken sandwich.
📖Why My Recipe Works
- Roasting red onions reduces their sharpness and allows the sweetness to shine. If you find raw red onions too harsh, then these baked red onions are for you!
- Add additional flavors like lemon zest, hearty fresh herbs (I like thyme), or even spicy dried chilis.
🧾Ingredient Notes
- Red Onions- This recipe works with any type of onion not just red onions. Cut the onions into a wedge shape or rings.
- Oil- Roasted onions are easy to make in the oven using a neutral oil like olive oil, filtered coconut, or avocado oil. And yes, even melted butter.
- Don't forget to pick up additional items for bigger flavor.
⏲️How to Make Roasted Red Onions
Start by preheating the oven to 400 F degrees.
- Don't cut less than a ¼ inch thick or they will burn.
- Parchement is optional. Lay the onion slices in a single layer and brush both sides with oil. Season as desired.
- Flip the onions halfway through so that they roast evenly. Let the onions roast until tender and caramelized, around 15 to 20 minutes. You'll know they're done when they're fork tender and the edges are browned.
How to Make Balsamic Roasted Onions
This is a special variation of this recipe that I love to make, but I didn't think it was different enough to warrant its own recipe.
- To make, mix the leaves of 4 fresh thyme sprigs (or ½ teaspoon of dried thyme) with 2 tablespoons each of balsamic vinegar and olive oil.
- Brush (or drizzle) the onions before baking. Flip halfway through the baking (still 15 to 20 minutes total) and brush (or drizzle) on an additional 2 tablespoons of balsamic vinegar.
How to Use Roasted Onions
As a side dish, I recommend the balsamic style.
For breakfast, mix it into scrambled eggs or my broccolini frittata recipe. Or chop up the onions with fresh herbs and mix into cream cheese for a roasted red onion bagel spread.
On tacos, I really like these onions as a condiment paired with my citrus-shredded beef, pollo asado, or BBQ shredded beef.
Chopped and mixed with refried beans and cheese for vegetarian bean tacos.
👩🏻🍳 Expert Tip
Once out of the oven, let the onions sit for a couple of minutes. This gives the sugars time to settle, enhancing their sweet, rich flavor.
Did you enjoy making this recipe? Show it some love with ⭐⭐⭐⭐⭐ and leave a comment! Hungry for more? Get more flavorful recipes!
📖 Recipe Card
Roasted Red Onions
Ingredients
- 2 red onions
- 2 tablespoons olive oil or coconut oil
- kosher salt and pepper
Instructions
- Preheat oven to 400 F degrees. Line rimmed baking sheet with parchment paper or lightly brush with oil.
- Cut onions into ½ inch slices. Arrange onions on a baking sheet. Brush lightly with oil and season with salt and pepper.2 red onions, 2 tablespoons olive oil or coconut oil, kosher salt and pepper
- Roast until caramelized and tender, 15 to 20 minutes. Flipping once halfway through.
Notes
- Store roasted onions in an airtight container in the refrigerator for 3 to 5 days.
- Roasted onions can be eaten cold or warmed up in the microwave or in a nonstick skillet.
- Balsamic- Add one tablespoon of age balsamic vinegar to the olive oil for extra caramelization.
- Garlic- Add 4 peeled whole cloves of garlic when roasting. Smash and mix with the onions after roasting.
- Fresh Herb- Add 6 sprigs of fresh thyme when roasting. Remove woody stems before serving.
Brandy says
With cooked sliced potatoes!!!!
Jen says
Sounds good!
Soniya says
Oven roasted onions are amazing.. it's been a long time I have made some... Definitely making them again tomorrow
Erika says
These roasted red onions are so flavorful.
Deanne says
We used this as a burger topping and as a salad addition. Yum!
Jen says
Perfect!!!
BCanning says
We only had sweet onions on hand and this recipe worked just as well as red. They were our veg of choice with lamb chops.
Jen says
Mmmm lamb chops. Glad the recipe was a good match.
Jen says
One of my favorite easy to make burger add-on