I haven't put them out just yet. I am waiting for the 'onion snow', folk lore about when you should start planting the early things like onions, cabbage, spinach etc. I dont believe you get much of a head start by starting onion seed indoors.
Onions can take the cold weather, so putting them out this time of year won't hurt them as long as the ground can be worked. I have left bunching onions out there year round, and had a crop in early April. I have also planted a row or two of bunching onion seed in the fall for the spring crop.
I was in Tractor Supply the other day and was checking out the Onion Sets but I decided to give it a couple of more weeks. Even though with this winter they probably could go out now.
In any case, cold weather won't hurt Onions. Or Garlic for that matter.