Marinated Roasted Onions

4.79 from 42 votes

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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.

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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!

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151 Comments

    1. I couldn’t truthfully answer that as I have never tried it that way Natalie. If you do try it that way I’d love to know how it turns out.

  1. 2(ish) questions:
    1. I have to prepare these to a point where they only need about 30 minutes of cooking because our turkey takes up the whole oven. (It’s 20+ pounds and has to be perfectly centered or the rack collapses.) Once the turkey comes out, all of the sides–and ham–go in. I know it’s not ideal, but can I cook these most of the way?
    2. I want to toss in a bunch of garlic cloves. Should I marinate them as well? (Why not?) Will they cook okay or might they burn on the outside and remain raw inside? If so, any tricks to avoid that?

    1. I think that would be fine pre-cooked and then finished off later Jill. As for the garlic, that sounds like a great idea and I would roast them with the onions from the start.

      1. 5 stars
        Thanks, Kevin. It came out great. I doubled the recipe and used smaller onions to reduce cooking time. I used less vinegar as someone suggested. (My husband’s family prefers plain, boiled onions. Every year I try to make some changes–sometimes I go too far.)

        The cooking method worked well. Creamy inside, indeed! I tossed in 2 1/2 bulbs of peeled garlic. They oddly turned purply blue, but they tasted fine. My husband ate the leftovers 4-5 hours after Thanksgiving dinner–literally sat down to a small bowl of the onions and garlic. I asked him if he liked it. He said it was good, “But I like my boiled onions.” Sheesh. Well, at least he’ll try almost anything.

      2. So happy to hear this Jill and at least he tried them, right? Thanks for taking the time to come back and let me know. 🙂

  2. 5 stars
    Never cooked anything with onions as the main ingredients except fried onion rings. These onions seem so right for my flu right now 😅 – Natalie

  3. Love roasted onions and your marinated ones sound wonderful…can’t wait to give them a try.

    1. Excellent, love to read comments like this Danielle. It’s always a big hit around our place during the holidays for company, but we eat them year round. Thanks!