Simple Roasted Onions

5 from 29 votes
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These simple oven-roasted onions are tender, mellow, caramelized, and require no peeling! Baked as halves, whole, or quartered to serve as a versatile side and on your holiday table!

A plate with roasted onion halves

I love to have multiple roasted vegetable side dishes to hand that I can rely on for meal prep, special occasions, or even simple mid-week meals. I’ve already shared recipes for roasted broccoli and cauliflower and maple/honey-roasted carrots. Now it’s time to share how to roast onions!

These oven-roasted onions are tender (almost creamy) in the middle with a mild, caramelized, subtly sweet, slightly crisp top and gentle infusion of fresh thyme flavor and have become a new favorite side (though roasted garlic is still my favorite roasted ingredient ever!).

Hand holding half a roasted onion

Not only is the onion side dish easy to prepare but it also stores well – you can meal-prep it for several days and keep it in the freezer for up to 12 months! Plus, the onions won’t be out of place on your holiday table either, alongside all your Thanksgiving/Christmas favorites, like creamy mashed potato, green bean casserole, brown gravy, etc.

Furthermore, I’ve included methods for how to make whole roasted onions, halved pieces, and quarters, depending on what works best for your dish. And if you want to explore other methods of enjoying onions, check out my recipes for caramelized onions, pickled onions, crispy fried onions, and even onion powder!

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The Ingredients

This roasted onion recipe requires just a handful of ingredients with plenty of options for versatility. I’ve used:

  • Onions: I used unpeeled medium yellow onions. However, this method should also work with red onions or white onions.  
  • Oil: I used extra virgin olive oil, though any neutral cooking oil will work.
  • Sea salt: added to taste. You can also add black pepper if desired.
  • Lemon thyme: to help infuse the baked onions with extra flavor.
Ingredients for roasted onions

Optional Add-ins and Variations

  • Balsamic vinegar: drizzle a tablespoon over the onions before baking for delicious balsamic onions. It also pairs wonderfully with the thyme roasted onions.
  • Sumac: a sprinkle of sumac tastes wonderful with the onions.
  • Other herbs: rosemary is another favorite of mine, and perhaps oregano or sage (or a combination of several, finely chopped) would work great too.
  • Butter: alongside the oil, add some melted butter for extra richness or make whole roasted onions, each with a tiny pat of butter.
  • Garlic: sprinkle them with a bit of garlic powder for extra flavor. Alternatively, gently press fresh garlic into each onion half to infuse the flavor throughout.
  • Other vegetables: there are several veggies you could combine with this baked onion recipe, including roasted potatoes, peppers, etc.
  • Parmesan cheese: serving the baked onions with cheese may sound odd but is actually delicious.
  • Sweetener: to enhance the natural sweetness from the roasted onions, you can add a small drizzle of a liquid sweetener – honey, agave, maple syrup, etc. Alternatively, you could sprinkle them with brown sugar in the last 10-15 minutes of baking.

How to Roast Onions? (Halved)

First, preheat the oven to 350ºF/180ºC.

Then, slice the onions in half. There’s no need to peel them (unless you prefer to at this point).

Onion cut in halve on a chopping board

Next, place the fresh thyme into a large oven-safe dish or rimmed baking sheet (by placing it UNDER the onions, it won’t burn in the process). Then drizzle olive oil over it.

Next, spread the onion halves, cut-side down, and sprinkle the entire dish with a bit of salt.

Then roast in the oven for 40-45 minutes, until the onions are tender and wonderfully caramelized/golden brown.

Steps for roasting onions

The exact baking time will vary based on the size of the onions you’re using, so keep an eye on them. You can check if they’re tender with the tip of a sharp knife.

Whole and Quartered Baked Onions

For quartered onions/onion “wedges”: the method is similar, but peel them first if preferred. Then roast for 30-35 minutes. Flip halfway, so both cut sides have contact with the pan and air.

Whole roasted onions: peel most of the layers of papery skin from the onions except the final one. Cut off the very end of the root end (so they can stand up in the parchment-lined baking dish) and about 1/2 inch/1 cm from the other side, then drizzle with the oil/seasonings and bake for 60-80 minutes (the time will vary based on the size of the onions). If the onions brown too quickly, you can cover the dish with foil.

Freshly roasted onions in a pan

How Make Ahead and Store?

Store: allow the roasted onions to cool, peel them, transfer any leftovers to an airtight container/bag, and store them in the refrigerator for 3-5 days.

Freeze: when properly stored, cooked onions can last almost indefinitely in the freezer. However, I recommend using them within 10-12 months. Start by flash freezing them until solid, then transfer them to a freezer-safe container/Ziplock style bag (squeezing out excess air).

Allow them to thaw in the refrigerator overnight before enjoying/reheating. They’ll last an additional 2-3 days after thawing.

Reheat: you could reheat the onions in the microwave or chop them up and reheat them on the stovetop.

Serving Recommendations

These oven-roasted onions will also work well when cooled and added to salads or as part of your roast dinner, at Thanksgiving, or Christmas!

Close up of roasted onions on a plate

Recipe Notes and Tips

  • Use similar-sized onions: that way, they’ll roast evenly.
  • Roasting time varies: depending on the size of the onions and if they’re much smaller/larger than the ones I use.
  • Avoid overcrowding: this will ensure the onions become wonderfully caramelized rather than just steaming from proximity.
  • Be careful not to overbake: otherwise, the onion can become dry and/or burned.
  • Remember to peel: I find it easiest to do so after roasting the onions. However, you can do it beforehand if preferred. Don’t attempt to eat the papery skin, though, as it won’t be pleasant.

Simple Vegetable Sides

If you try this oven-roasted onion recipe, I’d love to hear your thoughts and/or questions below. Also, I’d appreciate a recipe card rating below, and tag me in your recipe recreations on Instagram @Alphafoodie!

Simple Roasted Onions (Whole, Halved, Quartered)

5 from 29 votes
By: Samira
These simple oven-roasted onions are tender, mellow, caramelized, and require no peeling! Baked as halves, whole, or quartered to serve as a versatile side and on your holiday table!
Prep Time: 5 minutes
Cook Time: 45 minutes
Total Time: 50 minutes
Servings: 12

Ingredients 
 

  • 6 onions medium; yellow, white, or red.
  • 3 Tbsp olive oil extra virgin; or other neutral cooking oil
  • 0.2 oz fresh thyme few sprigs; or lemon thyme, rosemary, sage, oregano
  • 1/8 tsp sea salt and black pepper, if wanted; adjust to taste

Instructions 

  • Preheat the oven to 350ºF/180ºC.

Halved Onions

  • Slice the onions in half. There's no need to peel them, unless you prefer to, at this point.
  • Place the fresh thyme into a large oven-safe dish or rimmed baking sheet (by placing it UNDER the onions, it won't burn in the process). Then drizzle olive oil over it.
  • Spread the onion halves, cut-side down, and sprinkle the entire dish with a bit of salt.
  • Then roast in the oven for 40-45 minutes, until the onions are tender and wonderfully caramelized/ golden brown.
    The exact baking time will vary based on the size of the onions you're using, so keep an eye on them. You can check if they’re tender with the tip of a sharp knife.

Quartered or Whole Onions

  • For quartered onions/onion "wedges": the method is similar to the above, but peel them first if preferred. Then roast for 30-35 minutes. Flip halfway, so both cut sides have contact with the pan and air.
  • Whole roasted onions: peel most of the layers of papery skin from the onions except the final one. Cut off the very end of the root end (so they can stand up in the parchment-lined baking dish) and about 1/2 inch/1 cm from the other side, then drizzle with the oil/seasonings and bake for 60-80 minutes (the time will vary based on the size of the onions). If the onions brown too quickly, you can cover the dish with foil.

How Make Ahead and Store?

  • Store: allow the roasted onions to cool, peel them, transfer any leftovers to an airtight container/bag, and store them in the refrigerator for 3-5 days.
    Freeze: when properly stored, cooked onions can last almost indefinitely in the freezer. However, I recommend using them within 10-12 months. Start by flash freezing them until solid, then transfer them to a freezer-safe container/Ziplock style bag (squeezing out excess air).
    Allow them to thaw in the refrigerator overnight before enjoying/reheating. They'll last an additional 2-3 days after thawing.
    Reheat: you could reheat the onions in the microwave or chop them up and reheat them on the stovetop.

Video

Notes

  • Use similar-sized onions: that way, they’ll cook evenly.
  • Roasting time varies: depending on the size of the onions and if they’re much smaller/larger than the ones I use.  
  • Avoid overcrowding: this will ensure the top of the onions become wonderfully caramelized.  
  • Be careful not to overbake: otherwise, the onion can become dry and/or burned.
  • Remember to peel: I find it easiest to do so after roasting the onions. However, you can do it beforehand if preferred. Don’t attempt to eat the papery skin, though, as it won’t be pleasant.
Optional Add-ins:
  • Balsamic vinegar: drizzle a tablespoon over the onions before baking.
  • Sumac: a sprinkle of sumac tastes wonderful with the onions.
  • Other herbs: rosemary, oregano, or sage (or a combination of several, finely chopped) will work great.
  • Butter: alongside the oil, add some melted butter for extra richness or make whole roasted onions, each with a tiny pat of butter.
  • Garlic: sprinkle them with a bit of garlic powder for extra flavor. Alternatively, gently press fresh garlic into each onion half to infuse the flavor throughout.
  • Other vegetables: you can combine this recipe with roasted potatoes, peppers, etc.
  • Parmesan cheese: serving the baked onions with cheese may sound odd but is actually delicious.
  • Sweetener: to enhance the natural sweetness from the roasted onions, you can add a small drizzle of a liquid sweetener – honey, agave, maple syrup, etc. Alternatively, you could sprinkle them with brown sugar in the last 10-15 minutes of baking.
Check the blog post for serving recommendations and more top tips!
Course: Side
Cuisine: American
Freezer friendly: 10-12 Months
Shelf life: 3-5 Days

Nutrition

Calories: 53kcal, Carbohydrates: 5g, Protein: 1g, Fat: 4g, Saturated Fat: 1g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 3g, Sodium: 27mg, Potassium: 83mg, Fiber: 1g, Sugar: 2g, Vitamin A: 24IU, Vitamin C: 5mg, Calcium: 15mg, Iron: 1mg

Nutrition information is automatically calculated, so should only be used as an approximation.

5 from 29 votes (27 ratings without comment)

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Recipe Rating




6 Comments

  1. Myst says:

    5 stars
    These are absolutely AMAZING! I use it for Shallots, halved and peeled, with the Agave Syrup and the Balsamic Vinegar additions. Then add a tiny little sprinkle of demerara over each half towards the end. They smell like heaven! I’ve mainly used them diced in Mediterranean Savoury Muffins (though not all of them make it into the mix lol!), but I’ve also used them in my risottos, pasta sauces, pizzas and more and every time the people I’ve cooked for have told me its the best version of that meal I’ve made! They are such a delicious change to your regular plain shallots/onions. Thank you so much for this recipe!!!!!!!

    1. Support @ Alphafoodie says:

      So happy you liked the recipe, Myst! Adding the Demerara sugar sounds amazing!

  2. Mubarak says:

    Hello, I’m thinking about using this in my jollof rice to help acquire a woody/smoky taste by using oven roasted onions. Do you think this would work?

    1. Support @ Alphafoodie says:

      Hello!
      It will be a great addition 🙂

  3. Mac says:

    5 stars
    Absolutely delicious! Highly recommend

    1. Support @ Alphafoodie says:

      Thank you so much for your comment, Mac!