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. 5 stars
    I have made many of your recipes and we (family) just love them. Can’t wait to make this one! Looks amazing

  2. 5 stars
    I’m def making these. This is my most favorite idea ever. These sound absolutely divine. I absolutely cannot wait to make these. What a great combo with the brown sugar and the red wine vinegar. Love, love love this Kevin!!

    1. You’re going to love these Danielle. The insides get creamy soft and the slightly charred exterior is slightly tart and caramelized. Such great flavors! I’ve made with red onions too. So good. 🙂

  3. 3 stars
    Followed recipe exactly as printed. The onions even looked exactly like the photo. However, the cooked onions tasted too vinegary. Maybe less red wine vinegar or more water or more brown sugar to tame the tartness? I was thinking of trying it again with 1.5 cups of chicken broth, 1/4 cup water and only 1/4 cup of red wine vinegar and a bit of Worcestershire sauce for some zing.

    1. The tartness of the vinegar with the mellow, rich flavor of the slow roasted onions are what I love, but feel free to adjust to suit your tastes. Let me know how your next batch comes out, like your idea. Cheers!

  4. I am a newbie in the kitchen. Probably a stupid question, when u say trim ends, do you mean to cut the ends so that they have flat ends and can sit?

  5. 5 stars
    This recipe turned out great for me. Made these twice now for dinner parties, and my guests loved them. Not understanding the below commenter (Simon), unless he varied from the recipe. Maybe he didn’t keep the skins on?

    1. I think that might have been the issue, but not sure about the other part. Thanks for stopping by and letting me know Kenny. These always come out great, we love the flavor and you just need to be careful not to over cook them, right? Cheers! 🙂

    2. Could they have wrapped the onion with foil on the outer layer since the skin was remove? Would cooking it work then?

  6. 2 stars
    This is a shockingly bad recipe. I followed it exactly. The onions don’t stay together, they go straight to black, and you end up eating sour pickled onions. Shudder. Will never follow a Kevin recipe again.
    Almost all the comments here merely talk about how they LOOK great. Has anyone actually made them like me? Doubt it.

    1. Sorry to read that was your experience Simon. I hope you read the recipe correctly and kept the skin on the onions until AFTER cooking them, it is crucial and keeps them from falling apart. Other than that, I and others make this often and have never had BLACK onions. As you can see here your comment was approved because I have no issue with people having a problem, leaving a comment and hopefully I find a solution so others can read and learn too. If you read the above comment, he (Kenny) had no issue and makes them with success.

  7. 5 stars
    Fantastic! I added a bit of bread and butter pickle brine, Worchesteier sauce, red pepper flakes, clove and a pinch of mustard seed to my marinade, it was amazing. What was exquisite was the left over onions that I made into breakfast by putting them into grease muffin pan and pouring a eggs over them. I then topped them with some gruyere half way through baking. I topped my with loxs but not all my guest were salmon fans. Oh well their loss more for me.

    1. Hahaha I wrote before reading your response. Sorry! Don’t know how I missed it. I am eating them right now with sous vide chicken breast in a simple tomato sauce, because that’s what I was having anyway. Poured the marinade into the sauce and it is amazing. Thinking of separating the outer two layers and stuffing them with shark tartar (with avocado, fennel, jalapeño and green apple) as appetizers.

    1. In my opinion marinate and keep them covered and refrigerated, but don’t roast them if doing ahead. Unless it’s an hour or so. I feel the texture wouldn’t be the same. I have had leftovers and they are delicious, but fresh from the oven is best. Let me know what you think Alexander. Cheers!

    1. Hi there Peter! I use either white or yellow onions for this one. I have actually used red as well, but used white here in these photographs. All work exceptionally, but I lean more to the white personally. Hope this helps!