Simple Oven Roasted Onions Recipe + Video

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Roasted Onions in tangy rosemary dressing is a go-to dish that’s ready in under an hour. Scrumptious, caramelized baked onions are easy to make with this recipe!! Oven-roasted onions are the perfect dish for your holiday table and a great addition to any low-carb diet. 

bowl of rosemary roasted onions, perfect side dish for chicken


It’s no secret that caramelized onions are delicious on burgers and sandwiches and in French onion soup, but they are just as incredible on their own.

You can even add them to mac and cheese!

Explore different ways to use this layered root vegetable — it’s the foundation of many delicious sauces and can be enjoyed as a more prominent addition to your meal.

Not only does this make an easy side dish, but adding the fresh rosemary takes the flavor to all new heights.

This is the best way to get the best flavor out of your onions, in my humble opinion. 

ingredients for oven roasted onions

Roasted Onions

Tender and sweet, these baked onions are caramelized to perfection and boast rich flavor from a homemade Dijon dressing. 

Fresh sprigs of rosemary and bright lemon juice help round out the flavors, making this simple roasted onions recipe one that you’ll want to keep!

slicing onions for roasting

Roasted Red Onions Tips and Tricks

  • Use fresh herbs. You can often substitute dried rosemary when making recipes, but for oven roasted onions, fresh sprigs make all the difference. 

    Be sure to remove the stems and chop the leaves to help release their flavor and aroma!

You can also add sea salt and black pepper for an extra burst of flavor.

The addition pairs nicely with the sweetness of the onions, but still is a perfect addition for the onion halves or slices. 

  • Tip to avoid teary eyes: There have been numerous tricks shared throughout the years, from wearing goggles to slicing near running water. 

    The newest tip for cutting onions is to hold a chunk of bread or a cracker in your mouth, letting it hang out as you chop. 

    I can’t guarantee it will work, but it’s worth a try! 
  • Get your hands dirty! You can use spoons to toss the dressing into the vegetables, but honestly, hands really are the best tool for the job. Once you have all the simple ingredients combined, you can add the coated onions to the baking dish and hot oven. 
dressing for roasted onions in a bowl

How To Cut An Onion Into Wedges

  1. Trim.

    First, trim both the root and stem sides of the onion.

    You’ll often see dried brown roots on one side — slice off enough to remove these, but leave the thick white nub intact. This prevents the layers from separating.
  2. Peel and slice.

    Remove the peel and the outer layer (or two) if it appears dented or damaged. Slice in half through the stem, then in half again to make quarters.

This method words for larger onions and small onions. 

Kitchen Tools You Will Need

  • Rimmed Baking Sheet – Used for anything from cookies to roasting, a good baking pan will last for years.
  • Quality Knives and a big solid Cutting Board make prepping a breeze and are well worth the investment.
  • Citrus Juicer – This gets every last drop out, which makes juicing lemons so much easier.
pouring dressing over sliced onions

Roasted Onions FAQ

What goes well with roasted onions? 

This easy roasted red onions recipe pairs wonderfully with meat and poultry dishes. Enjoy with a simple weeknight dinner, or add it to your holiday menu, doubling as needed for extra guests.

It’s especially delicious alongside a beef roastpork tenderloin, or any main course that could use a tangy and sweet side dish.

Which onion is best for roasting? 

The general rule for onion varieties is this: red is the best raw, white is used to flavor dishes, and yellow is the most versatile for cooking.

That said, there are always exceptions to the rule. When paired with herbs like rosemary or parsley, the sharp flavor of red onion is muted, and it caramelizes perfectly in this roasted onions recipe!

What can I make with a lot of onions? 

Baking the onions is my recommendation! If you need to use them quickly to prevent spoiling, dice and freeze them for up to 3 months! Then you can use toss them into soups or skillet meals whenever you want to.

Or, make a pint’s worth of caramelized onions in a crockpot.

I also love having thin slices of onions to pair with meats and other main entrees. You can place onions directly ontop of the meat for flavor! 

Onion lovers will agree that the variety of onions offers os much flavor and taste. No matter what type of onion that you use, you’ll love the variety of flavors to make simple side dish recipes. 

roasted onions in baking dish

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rosemary and garlic roasted onions closeup - perfect side dish for chicken

Simple Oven Roasted Onions Recipe + Video

Donna Elick
Roasted onions in tangy rosemary dressing are a go-to dish that’s ready in under an hour. Baked onions are easy to make with this recipe!
5 stars from 1 review
Tried this recipe?Please comment and review!
Prep Time 10 minutes
Cook Time 45 minutes
Total Time 55 minutes
Course Side Dish
Cuisine American
Method Oven
Servings 6 – 8


  • 2 medium red onions
  • 1 medium sweet yellow onion
  • 1/4 cup extra virgin olive oil
  • 1 lemon, juiced
  • 1 teaspoon Dijon mustard
  • 3 cloves garlic, minced
  • 2 sprigs fresh rosemary, stems removed and chopped
  • 1 teaspoon kosher salt
  • 1/2 teaspoon freshly ground black pepper


  • Preheat oven to 400° F.
  • Trim onion both the root and stem sides of the onion. Be sure to leave the root intact (cut so that the dried brown roots are cut off and only a white nub remains).
  • Peel onions. Place onion with the cut side down on a cutting board and cut into wedges.
  • Place onions onto a baking pan. Set aside.
  • In a medium bowl, combine olive oil, lemon juice, mustard, garlic, rosemary, salt and pepper. Whisk until well combined.
  • Pour the dressing over the onions and toss well. You can use spoons, but I think hands are the perfect tool for this job.
  • Bake onions for 30 to 45 minutes, until tender and browned. Toss the onions once during cooking.
  • Remove from the oven, toss again, and transfer to a serving bowl.
  • Serve and enjoy!



Serving: 1serving | Calories: 116cal | Carbohydrates: 9g | Protein: 1g | Fat: 9g | Saturated Fat: 1g | Sodium: 403mg | Sugar: 4g | Fiber: 1g | Calcium: 24mg | Iron: 1mg

All nutritional information is based on third party calculations and is only an estimate. Each recipe’s nutritional value will vary depending on the ingredients used, measuring methods, and portion sizes.

Tried this recipe?Let us know how it was!
Rosemary Roasted Onions close up

Originally published August 2011, updated and republished January 2024

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  1. I love onions, too and this looks wonderful. The dressing by itself sounds great. One of my daughters just decided that onions that are cooked are actually pretty good, but the other one won't touch them. This is a great side dish – love it!

  2. What a simple yet wonderful dish. My husbadn and I really love both onions and potatoes. Looks great !

  3. Oooh, yum! I've never thought about serving onions on the side – am wondering how that would go over here at the 365 house.
    Definitely worth trying. Thanks, Donna!

  4. I love this combination of flavors. I can't imagine just doing onions though. I usually roast other veggies or potatoes with them. Sam would be in heaven with just a pan of onions though. I'll have to try onions on their own, now that I have four million pounds of them here to use!

  5. YAY! I'm crazy about onions…and yes, I could totally eat them plain which is why this recipe is SO awesome! Thanks for inspiring me! Onions here we come!

  6. Lol I love Mary's comment—- you're not tired of them yet are you :p

    I am going to have to try this I just hope it works with fresh rosemary since that's all I have.

    Your pictures are beautiful!!

  7. roasted vegetables are wonders in themselves, add rosemary and you just blew me away love it. chicken picatta is the perfect pairing too- great dish. i like to say picaaaatttttta because it is fun that way.

  8. My husband just brought in a bunch of small-ish purple and yellow onions from the garden that would be perfect for this recipe!

  9. Though more of an onion festival, the flavors looks blending with each other creating an aromatic scenario here. Good to know this simple yet so enticing recipe.

  10. wow…yummy yummy…i can imagine how sweet the onion turns out when it is roasted….I love to put this in salads….

  11. 5 stars
    My husband was a little reluctant to try these, but we both ended up loving them! The dish ends up so beautiful too! A 10/10 side dish for a great dinner!

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