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!

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





  • 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. There’s no accounting for taste, right Kevin?! Not sure what part wasn’t flavorful for Jane below??? I LOVE these and came back AGAIN to get the recipe for our family dinner gathering this weekend. They are always a hit and so so good.

    1. So happy you enjoy this one. I love it because its not the everyday side dish. Appreciate you coming back to let me know!

  2. 3 stars
    I cooked as directed. Needed to cook longer even though my onions were medium sized instead of large. I found them bland and nothing special. I gave it 3 stars because some of my guests still liked them.

    1. Not sure how anyone could consider these bland, but to each their own. Thanks for giving these a go and glad you guests enjoyed them Jane.

  3. 5 stars
    This is an exceptional recipe. It accompanied a prime rib dinner, so I used red onions, as Kevin recommended, and Irish Kellygold butter. I spooned extra sauce onto the onions after plating them. Very flavorful but not over powering. And they were beautiful to behold, too. There were rave reviews from the ninewedding guests. The groom announced he could eat a whole plate of them!

    1. Now this made my day! Thanks for trying this one at such a special occasion and for taking the time to come back and let me know Susan!

  4. 4 stars
    Oh, Kevin, I just love your recipes, BUT this one I followed to the letter except I added one extra onion and the amt. of wine vinegar had my lips curing!! Very good flavor but I added a cup of chicken broth and shoved them back in the oven for a while to try and dilute the vinegar. That help some but the vinegar was still more than we wanted. I will make this again b/c I feel it has good “potential”. Next time I will decrease the wine vinegar to 1/2 cup. I could not give it 5 stars for that reason.

    1. So sorry the vinegar amount got you! You’re a first ever to say that, too. Thanks so much for enjoying the recipe and for coming back to let me know Deanna. These are one of my all-time favorite sides.

    1. I love that so many people who didn’t like onions were converted with this recipe. I love it, too! Thanks for coming back to let me know Aly. 🙂

  5. Hi! want to make this recipe for Thanksgiving, but due to limited oven space I’m thinking about trying it in an air fryer. Thoughts/recommendations?

    1. Actually I haven’t dabbled in the air fryer craze, but if you do, let me know and I can update the recipe card to reflect?

  6. 5 stars
    Hi! I’ve been making these on and off for the last 5 years. Everyone loves them, I love them. They are easy enough for weeknights and elegant enough for company and holidays. That little pat of butter makes a world of difference! This is a really great recipe!!!! Thanks Kevin…. P.S. I absolutely appreciate the calorie count on your recipes. It makes my life so much easier (and tastier!)