Marinated Roasted Onions
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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.
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.
Roasted Onion – Choosing the Right Variety
- 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!
- 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.
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.
Marinated Roasted Onions
Ingredients
Marinade
- 1 cup water
- 1 cup red wine vinegar
- 2 tbsp brown sugar
- 2 tsp fresh rosemary chopped
- 1/2 tsp kosher salt
- 1/4 tsp black pepper
- 1 pinch red pepper flakes optional
- 4 large onions (See Note 1)
Roasting
- 4 tbsp butter
- 1 tsp fresh rosemary chopped
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
- 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
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.
About to do this onion dish
How did it turn out?
Hi, do you think red onions would work?
If you try them let me know how they turn out! I would love to hear!
hello keven can these be froen after roasting as i am only one that really likes onions thank you
I have never frozen these to give an answer, but I would just make a smaller batch myself and roast. If oy udo freeze them, please let me know how thay are. I’m sure the texture will be quite different. Cheers!
Hi Kevin, these onions sound awesome,and I can’t wait to make them,I’ll definitely be adding the garlic as mentioned below.
I am so glad you enjoyed them! We love the around our house!
Yummy! I love this! a perfect side dish!
I could caramelize 10# of onions each week & my wife would eat them for breakfast, lunch, dinner, & snacks in between! So, I want to give a huge “THANK YOU!” for posting this recipe as it gave me the inspiration to work on a roasted onion dish.
I tried your recipe 3x in the past 2 weeks.
My 1st try followed your recipe as written. The red wine vinegar almost killed us. When the dish was roasting, the pungent smell of the vinegar wafting through the house had us running to open the windows. When we tried to eat the onion, we were so puckered we could barely open our mouths to wash away the overwhelming tartness.
My 2nd try substituted balsamic vinegar for the red wine vinegar & replaced the water with chicken broth. This was much better and quite tolerable, but I was still not satisfied.
My 3rd try substituted a Cabernet Sauvignon (slightly on the sweeter side of the scale) for the red wine vinegar & kept the chicken broth instead of the water. I also replaced all the seasonings (we have a huge rosemary plant in the front flower bed, so it wasn’t an issue with availability) with a sprinkling of a commercial salt-free fajita seasoning that is quite ubiquitous here in San Antonio, Texas. I also omitted the butter. The result was a heavenly dish that will be part of our rotation from now on! The red wine & chicken broth reduced to a syrup that spooned over the onions and really bumped up the flavor.
I gave your recipe only 4 stars because the original recipe was like trying to eat onion flavored lemons, but I also gave it 4 stars (instead of fewer) because it provided the framework & truly inspired me to experiment, with the result of creating a little bit of heaven. I don’t remember what I was searching for when I clicked on the link to your website, but I am extremely glad that I did. THANK YOU FOR POSTING IT!!!
Glad you re-worked it to your needs David.
David, Do you still use the sugar?
My mother loves loves Onions any kind any way and every time I find a recipe that is devoted to Onions I save it! Would you considering adding the Just A Pinch recipe box plug in to your site so me and my friends can add your recipes to our Recipe Boxes with ease?
Currently working with a developer on some recipe card updates! Thanks Gina. 🙂
I had leftover onions from a bag I bought. I made these the other day and cooked them yesterday. They are SUPER yummy! You really have to be an onion fan ( which I am). The flavors of the rosemary mixed with the vinegar and sugar is wonderful!
We must have the same palette! I just LOVE these and the flavors are outstanding. One of my fav sides!
Kevin:
These sound good! I usually use balsamic vinegar with onions, but I’ll give these a try.
Thanks for the recipe.
I think these would be good in a slow cooker. You could always transfer them to an ovenproof dish and broil until browned on the top. That would free up the oven for other things.
Thanks Charlie. Give these a try and I really like your slow cooker idea. 🙂
Hi Kevin! Just came across a recipe of yours on FB and following you This recipe sounds amazing and can’t wait to try. I just recently made a scalloped version of roasted onions with Asiago and cream. I never knew onions could be a “side dish”.
Wow, Asiago and cream sounds amazing with the roasted onions. Thanks for stopping by Sandy. Enjoy!