Probably could but it is very bulky, after I bought it I posted about the collar and someone not sure if it was a rep of the manufacture posted that it just fits in there (paraphrasing). I am going to try leaving the zipper down just slightly (which may lessen the warmth around the upper chest slightly) and tuck in the collar. Again it is very cozy undie.Can you simply tuck the collar under?
Anyone diving the thinsulate type material, is it worth the extra expense?