The only reason my buttons are inside right now is because im getting them back into laying condition for a guy that's getting them from me other wise they'd be outside again. if you winterise them or make sure they're not in a molt and their outdoor shelter is draft free AND they have buddies being outside is FINE.
Many people say they will die outside, and all ican say is dont knock it until you try it...mine were perfectly fine and even housed with coturnixs
Edited to add: Both of the hens that i brought back in were out for several weeks from end of summer until just a week ago. I live on the top of a mt, it gets disgustingly cold up here...several nights of below freezing and they were/are fine