For me, it would depend on the horse. If these are easier keeping QH's and the like, I would have no problem only feeding them them then having them out on the communal pasture for part of the day. If we are talking about hard keeper horses, the type that struggle to maintain proper weight even during the summer, I would have them in the paddock with 24/7 hay, preferably an alfalfa mix, and probably supplement with a high fibre/high fat concentrate, Step 8 or something similar.
I have done self board on pasture only over a few winters, and it's worked well for me. I also went out once a day to feed, and I didn't have a slow feeder net or box, but I found scattering the hay around in a different spot each day slowed down their eating, but they still cleaned it up well. There was a few weeks where I couldn't get hay, so I scattered alfalfa/timothy cubes for them instead, and while it definitely wasn't ideal or something I'd ever do for a whole winter, it worked just fine for a short time. I had a big TB who kept his weight fairly decently, I blanketed him and he got a scoop of Step 8 every day, and a little QH who could get fat on air basically, so no blanket or extra feed for him. They both came out of the winter in decent shape. They didn't have an actual shelter, but lots of trees and hills in the pasture for cover.
Allowing them out in the communal herd only when the weather is nicer is another option, say anything warmer than 20 degrees they can go out, anything colder, they stay in their paddock and just eat. Are you blanketing them at all?
The winters here can be harsh at times, but most horses do just fine. Growing up in northern Alberta we never blanketed anything, they lived with lots of trees as their shelter and ate off a round bale in the pasture. But very rarely did we ride in the cold weather. Of course if you want to keep riding regularly over the winter, an indoor is pretty much a necessity, and you'll most likely end up have to clip somewhat and blanket as well. So that all changes the game drastically as well.
Last edited by albertaeventer; 09-18-2013 at 12:15 PM.