Gardein brand vegetarian entrees are pretty tasty, but are the most annoyingly packaged food products I have encountered...the soy and wheat Tofurkey-like stuffed globes and any acompanying sauces and rice beds are all in plastic pouches that can only be sloppily opened, with scissors or knife...you will, to at least some small degree, be wearing your foodstuffs, which makes their utility as office lunches rather more limited than it needs to be.
The all-vegetarian The Green House in Collingswood, NJ, is currently my favorite Chinese vegetarian place in the area, and that's facing some stiff competition in Philly proper. It's also next to a fine Thai restaurant, the Thai Basil, if you or your party Must have some meat along with...they share an outer door. Excellent food, good service (if anything, too hospitable, but not in an intrusive way), and the only downside is the slightly repetitive AORish music piped in (not too loud). (856) 854-0896, and a nicely varied menu. They will refer to bok choi as greens.