Marinated Roasted Onions

4.79 from 42 votes

This post may contain affiliate links. Please read my disclosure policy.

These slow roasted onions are easy to make for a simple, flavorful holiday side. Make this recipe to serve with your holiday ham, turkey, or beef roast.

close up of baked onion halves with rosemary


This recipe is worth you taking a look at. Really. It’s not a typical holiday side dish like traditional French’s green bean casserole or roasted potatoes, but I bet you’ll love it just as much. The onions caramelize roasting in a bath of red wine vinegar, brown sugar and spices.

The result is a tender vegetable that’s soft and creamy on the inside and caramelized on the outside. The flavor is mellow and sweet, and it takes on the flavor of the marinade, making a memorable side on your holiday table.

These make it to our table more times than I can count because they don’t need a holiday reason to sing and are perfect with grilled meats when no holiday is the reason.

caramelized vidalias in baking dish

Roasted Onion – Choosing the Right Variety

  1. Best Onions for Roasting / Baking

Because this is a side dish recipe, the best option is to use an extra large variety of onion. You’ll be slicing them in half and leaving the skins on while they bake, so I recommend using a large, sweet variety like Vidalia or yellow. You could even use red onion, which also tastes fantastic caramelized!

close up: raw vegetable slices in baking dish- pats of butter on top
  1. Choosing a variety based on the protein you’re serving.
  • Poultry– If you’ll be serving the roasted onions with a roast turkey, I think yellow is your best option.
  • Pork– The best option to serve with a holiday ham is definitely Vidalias. Their sweetness pairs perfectly with glazed ham, especially if you’ll be using a slightly spicy glaze like chipotle orange.
  • Beef or Lamb– For boneless prime rib, lamb roast, or braised beef brisket, any type of onion works well. This is where making baked roasted red onions might be a great choice.

Video: Making Marinated Roasted Onions

The recipe is pretty simple and aside from the marinating, it’s really quick and easy to make. Watch the video in the recipe card to see the process from start to finish.

overhead: baked onions in round casserole dish

Planning Ahead

This roasted onions recipe is one you need to plan ahead for, as the onions need to sit and marinate overnight before roasting. While you’re at it, these Herb Roasted Potatoes could easily be made at the same time!

NOTE:
I’ve roasted onions without marinating, and they’re okay. But I feel the overnight soak really makes a difference. If you’re crunched for time and need to skip the overnight soak, at least let them marinate for an hour if you’re able to.

This is a rich and flavorful side dish, and it really does go well with nearly every protein you can think of. For a nice garnish and punch of flavor, I occasionally add fresh chopped rosemary during the last 5 minutes of baking time.

Still Hungry?

Subscribe to my Newsletter, follow me on Facebook, Pinterest, Instagram and YouTube for all my latest recipes and videos.

This post, first published on Kevin Is Cooking November 2017, was last updated with new content on Sept. 11, 2021.

close up of baked onion halves with rosemary

Marinated Roasted Onions

4.79 from 42 votes
These marinated roasted onions are easy to make for a holiday side dish. Make this recipe to serve with your holiday ham, turkey, or beef roast.
Servings: 8
Prep: 10 minutes
Cook: 1 hour
Marinate Time: 8 hours
Total: 9 hours 10 minutes

Ingredients 

Marinade

Roasting

Instructions 

  • Blend marinade ingredients in small bowl and pour into a baking dish that will hold all 8 onion halves. I use 8×8″ baking pan or round 12″ baking stone (pictured) depending on size of onion.
  • Trim the end of onions and cut horizontal (leaving skin on) and place cut side down in marinade. Marinate overnight covered in refrigerator.
  • Preheat oven to 400°F. Flip the onions over in the marinade, and lay on the flat bottom of each side. Top each onion with 1/2 tablespoon of butter and remaining teaspoon of rosemary. 
  • Roast uncovered in oven for 1 hour or until golden brown and tender, basting once or twice during roasting. Remove from heat, spoon reduced sauce over and sprinkle with parsley or more fresh chopped rosemary. Remove outer skins before eating and serve.

Video

Notes

  1. White, yellow, or red onion may be used. Trim ends off onions, slice in half horizontally, keeping the skin on to hold shape and protect the outside as it roasts. Just peel and discard the skins before serving.

Nutrition

Serving: 1oz | Calories: 90kcal | Carbohydrates: 8g | Protein: 1g | Fat: 6g | Saturated Fat: 4g | Cholesterol: 15mg | Sodium: 203mg | Potassium: 92mg | Fiber: 1g | Sugar: 5g | Vitamin A: 177IU | Vitamin C: 4mg | Calcium: 19mg | Iron: 1mg

The information shown is an estimate provided by an online nutrition calculator. It should not be considered a substitute for a professional nutritionist’s advice.

Course: side dishes
Cuisine: Melting Pot
Have You Made This Recipe? Let Me Know on InstagramTag @keviniscooking or tag me #keviniscooking!
titled image of baked onion with caramelized edges

Kevin

Whether in the kitchen or on the grill, you’ll find me cooking American favorites with a love for BBQ, Mexican and Tex Mex. I’m passionate about making tasty food because life’s too short to be bland!

Free Bonus
5 Secrets to True Tex Mex
Essential recipes & tips for delicious Tex Mex cooking!

email image

Explore More

Leave a comment

Your email address will not be published. Required fields are marked *

Recipe Rating




This site uses Akismet to reduce spam. Learn how your comment data is processed.

151 Comments

  1. I am definitely going to save this recipe to make over the weekend. I have a beautiful roast they would be perfect to serve with!
    Stunning pictures too

  2. 5 stars
    You are totally speaking my language with these onions Kevin! I think I could eat the whole entire pan! No shame. Perfect with a nice juicy steak! Happy weekend!

  3. 5 stars
    Kevin! I can’t even with this! I want to swim in that pan! I am a huge fan of onions. A huge fan of anything roasted. And a huge fan of all that you produce. Oh. My. God. That’s all.

    1. Thanks Annie, you are one of my reader and fellow food blogger friends that always puts a smile on my face! 🙂

  4. 5 stars
    Hey Kevin! We eat tons of onions and these will be on the table soon! These would be lovely as a side with Nagi’s leg of lamb she posted today! Can I include this in the “holiday” fare?

  5. They look great. Can’t wait to try. One question, your pictures show a pat of what looks like butter on each onion half but it isn’t in the recipe. I do think everything (at least most things) are better with butter so I thought I would ask. Should butter be in the recipe?

    1. I couldn’t agree more David! Updated to reflect, thanks for the eagle eye my friend! Hope you enjoy these.

  6. 5 stars
    Oh my! These are beautiful!! I can think of so many upcoming get togethers where these onions will impress…and vanish, but I also see these in my weekly menus, the overnight marinade sounds incredible and easy. Rosemary is one of my absolute favorite herbs, too. Two thumbs up!

    1. Thanks so much Sally, they’re a house favorite too. Just make sure, due to different sizes of onions, that they are tender as times may vary. 🙂

  7. What a delicious idea! I’ve never done marinated onions on the stovetop like this, but we love brushing thick-cut onions with herbs and olive oil and then tossing them on the grill. This sounds like the winter version of that one…and I definitely need this to happen soon! Love it!

    1. Awesome to hear, these are a fantastic side whether it’s a holiday dinner or not Dave. That vinegar mellows as do the onions slow roasting like that, but the flavor combo is wonderful.

  8. I’ve made roasted onions before, but these look SO much better! I can tell you one thing’s for sure….these are in my future. Can’t wait to try and love how all the onion layers opened up a bit. Onions are complex like that, lots of layers to their personality, lol 😉 And you know I’m all over this recipe ’cause of the vinegar. The rosemary at the end is a nice touch and pop of colour too. Pinning!

    1. Thanks Dawn, these get almost creamy inside, but hold their shape. I love the roasted edges and the surprising flavor from the vinegar is awesome. 🙂