Rehearsal Dinner Livingston/ West Orange
There are really no BBQ places in Livingston or West Orange. The closest that I know of that has great food is Indigo Smoke on Bloomfield Avenue in Montclair. I know that they do off-site catering, but im not sure that they have a room at the restaurant big enough to fit that many people. However, it is absolutely worth giving them a call to find out. Its an awesome restaurant.
For non BBQ food in Livingston, I would recommend Nero's on South Livingston Ave or Il Vicolo as coughy mentioned. They can both accommodate that many.