pg_dumpall and output formats?

When trying to dump all of our databases,

pg_dumpall -b -o -F t --f full_pgbackup.tar

We're getting:

pg_dump: large object output is not supported for plain text dump files.
pg_dump: (Use a different output format.)

So it would seem that the "-F t" isn't getting passed to pg_dump. The
option set does work fine when using pg_dump alone on a single database.
What am I doing wrong here?

Thanks,
John

--
John Madden
UNIX Systems Engineer
Ivy Tech State College
jmadden(at)ivytech(dot)edu