grep equivalent of the kwrite regex [A-Z][A-Z]+

So, it took me ages, but I finally learned to *think* in terms of regular expressions, thanks to using them in kwrite. But I still don't know how to translate that knowledge to grep. I love my grep, when I know what I'm doing with it, but the manual has always given me a headache. I'd like to match stuff like the following lines:

CAPITALSFOLLOWING anewline.
CAPI
TALSFOLL owing
ANEW line.

That is, lines that begin with two or more capital letters. But I can't figure out how. In kwrite, I would match these lines using: \n[A-Z][A-Z]+ But grep... hmm. I have a feeling like it's something like: me@ROOROO:~/$ grep "^[A-Z]something" filename but me@ROOROO:~/$ grep "^[A-Z][A-Z]+" filename doesn't work (returns an empty file). A google search for the term 'grep match one or more occurrence' lead me to believe that me@ROOROO:~/$ grep "^[A-Z][A-Z]*" filename was the right syntax. But, alas, that doesn't do the trick.