If you plant in the fall they will overwinter but instead of forming a bulb next year they will flower. So I wouldn't. You can keep the sets stored and plant a little at a time to use as green onions. No need to plant them all at once.

Rodney

Yes, sets make wonderful scallions. I've used mine up now, but planted them in groups of a dozen or so every week during most of April and May. I pull 2-3 a day for cooking.

At a local organic farm they don't even bother to "plant" them -- just roll the sets into prepared soil, and let them go. I tried it in a small area and it works great.

Onion sets may not be hardy enough to overwinter from a fall planting, and will not store well enough to be usable next spring. If you have the room plant them now, you may get small onions from them yet, and you will almost certainly get green onions.

Thank you all so much for the very helpful advice. I've planted a bunch and will do another row of them later this week for use as scallions.