I too think they would be fine outside assumingthat you give them a warm place to go on the cold nights. Anest box stuffed with hay is what we gave our bunnies to keep them warmon cold days when I was a kid. We also made sure they were ina place that would have some protection from harsh winds.This is why I was asking for your bunnies living conditions before Igave an answer.
*edit* Of course I prefer to have my bunnies indoors becausethen they can be all the more comfortable (no big temperature changes,no wind, no rain and snow, you know) and I am able to enjoy theircompany all the more when they live in the house with me. Iwould say, if you would like to share your life with them more, indoorsis the way to go.