Marinated Roasted Onions

4.73 from 43 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!

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

4.73 from 43 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





  • 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.



  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.


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


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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  1. 2 stars
    I liked the concept of this recipe but I think a whole cup of red wine vinegar is way too much. I would use a half cup at the most. The vinegar taste was so strong, I even cooked it for longer hoping it would cook down a bit more but it doesn’t cook off. I think Id like to see this recipe with less vinegar and a bit more brown sugar, next time I make this I will try halfing the liquid content.

    1. I’ve gotten “it’s bland” or “why keep the skins on” comment, but never too much vinegar. Being diluted 50/50 with the water and brown sugar, its a delightful flavor. To each their own. Thanks for trying and letting me know Ruby. 🙂