syntax of "find" - am I losing my mind?

I'm trying to find all files in my home dir that are not in group foo or
group bar.  Most of my files are in one or the other of these groups.

This is my tcsh command line:

    % find ~ -xdev \! \( -group foo -o -group bar \) -ls

This dumps out every file.  It should just dump out a few.  Why?

I tried replacing \! with -not and I tried replacing -o with -or.
Neither helped.

I'm sure I've done this sort of thing in the past (successfully).
--
"I think I understand delicate, but why do I have to wash my hands, and
be standing in cold water when doing it?"

    Kaz Kylheku <kaz@kylheku.com> in comp.lang.c