The present invention is directed to compounds of Formula I: ##STR00001## and Formula II: ##STR00002## (where variables R.sup.1, R.sup.2, R.sup.3, R.sup.4, A, B, G, J, Q, T, U, V, W, X and Y are as defined herein) useful as antagonists of CGRP receptors and useful in the treatment or prevention of diseases in which the CGRP is involved, such as headache, migraine and cluster headache. The invention is also directed to pharmaceutical compositions comprising these compounds and the use of these compounds and compositions in the prevention or treatment of such diseases in which CGRP is involved.