These easy roasted onions combine sweet onions with olive oil, butter, kosher salt, fresh ground black pepper, and fresh thyme and rosemary into a flavor-packed aromatic side dish. It is a must-try for all onion lovers and a regular roasted veggie at our house.
With just a handful of simple ingredients and a few minutes of preparation, this tasty vegetable recipe is a must-have for every good cook. I love serving this side with grilled steak and roasted chicken, but endless possibilities exist.
Ingredient Notes and Substitutions
See the complete list of ingredients on the recipe card below.
- Onions: preferably sweet yellow onions or Vidalia onions.
- Seasonings: salt and freshly ground black pepper
- Herbs: fresh rosemary, thyme, parsley
How to Roast Onions
This is just the nutshell version. See the recipe card below for complete directions.
- Cut the onions in half from the tip to the root, then remove the outer, dried layers. Arrange them in a single layer, cut side up, on a rimmed baking sheet covered with parchment paper.
- Drizzle with olive oil and top each half with a pat of butter.
- Sprinkle generously with kosher salt and fresh ground black pepper. Top with fresh thyme leaves and chopped fresh rosemary.
- Roast for 35-45 minutes or until golden brown. Sprinkle with more fresh thyme and rosemary.
Preparation Tips
- This recipe works with any number of fresh herbs. We love adding thyme, rosemary, Italian parsley, or whole cloves of garlic to the baking sheet.
- Parchment paper helps the onions brown better and cook more evenly. It is usually rated up to 420 degrees Fahrenheit, but check your box. As a bonus, it makes cleanup easy.
- These sweet treats are best served promptly, but can easily be heated again in the hot oven for about 5 minutes.
Serving Suggestions
I like to serve these onions with New York strip steak, air fryer salmon, or beef roast. For something different, try a big bowl of hearty soup like minestrone or meatball soup.
Roasted Onions
Ingredients
- 4 medium sweet yellow onions sliced in half from root to tip
- 3 tablespoons olive oil
- 2 tablespoons butter
- kosher salt
- fresh ground black pepper
- fresh rosemary chopped
- fresh thyme leaves
Instructions
- Preheat the oven to 400 degrees. Cover a small baking sheet with parchment paper.
- Cut the onions in half from tip to root then remove the outer dried layers. Lay them cut side up on the prepared baking sheet in a single layer.
- Drizzle with olive oil and top each half with a pat of butter. Sprinkle generously with kosher salt and fresh ground black pepper. Top with fresh thyme leaves and chopped fresh rosemary.
- Roast for 40-45 minutes or until golden brown and tender. Sprinkle with more fresh thyme and rosemary. For best results, serve promptly.
Notes
Nutrition
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Freya
These were so delicious served alongside a roast dinner, the roasting really sweetens the flavour so much!
Beth Pierce
Thanks Freya! So glad that you liked them!
Catalina
This will be my new favorite side dish. Onions are so good!
Michele
OMG! I can’t believe how good these sweet roasted onions tasted! I served them with a pot roast and got rave reviews! I’ll definitely be making these again.
Beth Pierce
Thanks Michele! They are so delicious with pot roast!
Toni
I love it! Such a perfect natural flavoring! Thanks so much for sharing!
Lauren
So deliciously sweet, we love them with roast chicken and some creamy mash.
Beth Pierce
Great choices! How delicious!
Amanda
These onions came out perfectly! They were so tender, and I love the extra flavor the rosemary and thyme added. Delicious and so simple!
Beth Pierce
So glad that you liked it Amanda!
Claudia Lamascolo
I had never roasted onions like this before until now and that made a fantastic flavor with that rosemary addition
Beth Pierce
Thanks Claudia! So glad that you liked it!!
Amanda
This is one of our favorite simple side dishes! So much flavor and so easy.
Erik
Wow this was so easy! Love the recommendation of serving it with burgers, too.
Beth Pierce
Thanks Erik!
Amanda
Oh my goodness I can only imagine how good this smells!