Efficient way of finding the through model.

Hey, I was wondering if there are any good ways of finding the joining
through model in a has_many :through association, without its id, only
the 2 models it is joining together. Maybe I just missed something,
but the only way I am able to do it is something like:

group.memberships.find_by_user_id(user.id)

The problem is, that is a query, and so I can't use it where it is
displaying a list of users or what not without killing my application.
I am hoping I am missing something stupid here, please say I am.

-Ray Morgan