Or use the sprouts as you would green onions.
Grandma used to say that storing onions and apples together kept the onions from sprouting. There is no concrete confirmation of that on the web, but it works for me. l also remembering one year when I stored some apples in the refrigerator where I was keeping some tulips, potted up for forcing to bloom about March. That year the tulips didn't do their usual thing. Finally I realized that one of the crisper drawers in that refrig was full of over ripe apples.
Here's a link with some speculation on the effects of ethelyne on onion growth.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2707281/#:~:text=Ethylene%20is%20known%20to%20inhibit,et%20al.%2C%201992).&text=Ethylene%20production%20of%20onion%20bulbs%20during%20dormancy%20and%20initial%20sprout,Rahman%20and%20Isenberg%2C%201974).

You wil find that the onions that have sprouted are likely to not be at their very best. Of course you can still use them and the green sprouts but the onion is not likely to be nice and firm anymore. You are likely to find that the onion has begun to separate and may be rather tough inside or the layers are separating. I don't usually use them if that happens but certainly would use them if I dont have any others.

It was a trend this year to put the bulb ends of green onions into a glass of water and let them regrow. I saw this somewhere in the last few days and was wondering why someone had green onions in a jar of water in the window. Then, I read about it being something that folks were doing.

They are fine to use but you need a plan to use them up. All the green sprouts are good. Just use like green onions. Garnish or soups. (last 5 minutes for soups.) Cut them off and wrap in a damp cloth or p-towel. Perfect use is a big batch of caramelized onions that freeze well for later.

They are marginally old stock. May have been stored properly but this is what happens unfortunately. I would take them all out onto your counter a grade them. Any not sprouting and firm should be ok for a week. Even in a bag and crisper drawer will help a bit though not ideal. Check for soft spots and mold.

Big batch of caramelizing is the best bet. (the only thing I use my old crock pot for) This way you can discard any cut open with a off color soft slimy layer. Firm, even fresh green is fine.

WedMorn. I've been doing that for years with green onion, celery, leeks...etc I always have some going year round.

Often, when there are sprouts, the interior becomes brown, I think from decay.

I recommend using those onions as soon as possible...Do you like onion soup, carmilized onions?

I saw recently (here?) a tip about making caramelized onions in a crock pot, which is what I would do if faced with a bag of sprouting onions.You can store the caramelized in the freezer. You can also saute and freeze, but that seems like way too much work for me if the other option is a few hours in the crock pot. I find after they sprout that they become soft and I would want to use or process asap.

Thanks, everyone! I had planned to cook up a big bunch of onions and peppers today!

I also had a big bag of onions from Costco that I caramelized in the crockpot this week. Mine were not showing any sprouting, but when I sliced them in half, several had little green shoots inside. I picked out the shoots and proceeded with the caramelization.

4-5 lbs of onion sliced (I used the slicing disk on the food processor)

3 or so Tblsp of EVOO

1/2 tsp salt

Toss all together in the slow cooker. Cook on low for 10-12 hours. Set lid ajar for the last couple of hours to allow juice to evaporate. Freeze in ice cube trays.

Below L-R: 6 hours, 9 hours, 12 hours.

Thanks, bbstx—love the photos & input!

I always use the shoots. They're tender and tasty, IMPE. I just trim off the tough or mushy parts.

I grow walking onions, which are like extra big hearty scallions, and use them all the way from top to bottom.

Thanks for chiming in here, Carol!

I tried caramelizing onions in the slow-cooker a number of years ago for French onion soup but they didn't turn out like that. Yours are gorgeous Sleeve. Mine had too much liquid and were still a tan colour after cooking all day long; similar to your second photo. But, I didn't crack the lid open, as the directions didn't say to do that.