Madcow2 said:
Simple answer, push on your squat, dead, row, press - add 15lbs of solid bodyweight (i.e. not all fat), your forearms will grow.
To say Madcow has a penchant for hitting nails on the head is as sure a statement as "the sun will rise tomorrow if the weather's clear (and you're not in that weird part of Alaska)"
Seriously, Dapit, I'm in much the same boat. My forearms and calves have both been around the same size for awhile.
Calves particularly frustrate me; I just can't get them over 18.25", and I want 19" so bad I can taste it. I keep making nice, regular strength gains, I train them
sorta frequently (3 times in a 2 week period), use very good form, etc.
But I've known all along what the problem has been: little overall weight gain. I'm just not going to get 19" calves unless I put on a good 12-15 pounds. I've been afraid to commit to that because I've not had the appetite nor comfort with the possibility of putting on several lbs. of fat.
So, we gotta literally swallow our pride

With a clean "bulk" and a little cardio you can minimize the fat gain, but it's time to put that food down the hatch and get bigger all over. Run your squats, rows, chins and pulls mad progressive, and as Tom suggested, you might try just a
bit of direct forearm work evenly-spaced throughout the week.
One good training cycle probably won't get you to 15", but you'll be that much closer!