I am looking for a mid-priced ($14 to $22/entree), highly rated
restaurant to hold a celebration party / function for 50 people at the
end of July in the greater Boston Massachusetts area: specifically
Boston, Cambridge, Watertown, Waltham, Newton, Belmont, and surrouding
areas.  I have looked at a number of restaurant review websites, but
none of them I have found have ratings, rankings, and reviews for
restaurants that can hold functions.  I would like preferably only
restaurants that have private function rooms (or sealed off areas),
and we are looking to avoid chain restaurants and hotel restaurants. 
In addition, we would like to avoid Asian, Indian, and other more
exotic restaurants (American, European, Italian, and similiar
restaurants would be fine).

Is Greek ok?

I personally love all different kinds of food (Greek, Asian, African,
Middle Eastern, Indian, etc), but I got marching orders to stay from
the more exotic kinds of food.

"Exotic" is totally relative, isn't it?  So the question was meant to
ask if you considered Greek "exotic."  There are some great Greek
restaurants in the area.

I'm really surprised that no researcher has weighed in on this one yet.

Apteryx
(not a researcher)