Almost every episode of Season 4 has some scenes outside of the campus. This really started at the end of Season 3, with the "Cocktails" and "Beach Games" episodes.
Season 1 is only 6 episodes and is entirely in office.
Season 2 is about 75% in office. The ones that spend a lot of time outside are Dundies, Booze Cruise, Email Surveillence.
Season 3 is about 60% in office. Convention, Diwali, Beach Games, Phyllis' Wedding, Cocktails.
Season 4 is about 50-55% in office. Dinner Party, Night Out, Job Fair, Survivor Man.
Season 5 and 6 about 75%.
Season 7 is in progress - Andy's Play drags the figure down.