To my ear, the former should be pronounced “vurb-ij” and the latter “fohl-ee-ij” (the endings may vary among “aj”, “edge” and “ij”).
I occasionally hear people say “vurb-ee-ij” and often hear “fohl-ij”.
Are they interchangeable? Regional?
According to Merriam-Webster and my own experience, the three-syllable versions of both words are the “more proper” ones. While the two-syllable version of verbiage is quite common, I rarely hear foliage with only two syllables (but this could be regional; see below). M-W marks two-syllable pronunciations of foliage as “questionable”. Here is an explanatory excerpt from M-W:
The disyllabic pronunciation \ˈfō-lij\
is very common. Some commentators
insist that foliage requires a
trisyllabic pronunciation because of
its spelling, but words of a similar
pattern such as carriage and marriage
do not fall under their prescription.
The pronunciation \ˈfȯi-lij\ is
disapproved because it suggests the
transposition of the l and i in the
spelling. It is not as common as
\ˈfō-lij\ and may be associated with
the nonstandard spelling foilage.