Mac Mail System 10.6.4

In the older version of the Mac system, I used to be able to drag an email address from an email directly into a group. Now I have 10.6.4 and can no longer do this. The idea is to select a large group (10-50) of addresses and directly add them to a contact group in my address book, rather than first adding them to my address book individually and dragging them from my address book into a group.