These Marinated Slow Roasted Onions are a side dish that are worth you taking a look at. Really. Not your typical side dish like a green bean casserole or a baked potato, these onions caramelize roasting in a bath of red wine vinegar, brown sugar and spices.
The result is a soft and creamy on the inside and caramelized on the outside onion that mellows in flavor and takes on the marinade to make a memorable side on the holiday table.
Roasted onions you say? Why yes, these Marinated Slow Roasted Onions are incredibly delicious and so easy to make and the aroma will get your mouth watering. I wanted to share with you a quick and tasty side dish today with all the upcoming holidays.
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.
Trimmed onions get sliced in half horizontally, keeping the skin on to hold shape and protect the outside as it later roasts. Then marinade overnight, dab with some butter, chopped rosemary and slow roast in the marinade. Heavenly!
This one you need to plan ahead for as the onions marinate overnight before roasting. While you’re at it these Herb Roasted Poupon Potatoes could easily be made at the same time!
I’ve made them without marinating and feel the overnight soak really makes this rich and flavorful. I occasionally add fresh chopped rosemary at the last 5 minutes of roasting for an added punch of flavor. Enjoy!
This recipe first appeared on Kevin Is Cooking November 2017 and has been updated with a new video.
Marinated Slow Roasted Onions
Ingredients
Marinade
- 1 cup water
- 1 cup red wine vinegar
- 2 tbsp brown sugar
- 1 tsp fresh rosemary chopped
- 1/2 tsp kosher salt
- 1/4 tsp black pepper
- pinch red pepper flakes optional
- 4 large white or yellow 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 8x8" 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 wide 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, 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.
Notes
Nutrition
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… Read more »
Glad you re-worked it to your needs David.
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!
Hello! Do you cook covered or uncovered?
You would roast these uncovered Shannon. Enjoy!
Can I use a different herb than Rosemary? They are not big fans of it in my house.
Thyme would be my next for sure Lisa. Let me know what you think. Cheers! 🙂
Question:
Can the sugar be omitted and still have good flavor?
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.
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?… Read more »
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.
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… Read more »
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. 🙂
Have you made with sweet onions? Does it have a good flavor, or is it less appealing using this method?
I have and loved that as well Lise. Sweeter than savory, but quite tasty. 🙂
Have you ever roasted chicken, carrots or potatoes on top of the onions while they cook?
No, but that sounds like Sunday’s dinner! Thanks Mel. 🙂