Moving all PCs in Security Group to a different OU

Hi,

We have some student PCs that we sometimes need to change the internet settings for.  To do this we move them to a different OU with a different GP.  This works fine as long as I do it manually but there are 80 PCs and after an exam I need to move them back again.  I have all the PCs in a security group, what is the easiest way to move all the PCs in this group to the new OU?  When I see the PC members in the group I can't right click on them and move them.

Many Thanks,

Stephen