Mediterranean food naturally has good vegan/vegetarian options...so Olive House is always a good choice when you want more than 1 option.
I've had the hummus, and falafel wrap with lentil soup. All of it was delicious, and as far as I can tell it was vegan. The staff is really kind, and I'm sure are willing to answer any questions regarding what is in the food. There is a whole section dedicated to vegetarian options, so it should be easy enough to figure out if there happens to be any diary/eggs in those options.
Updated from previous review on Friday July 05, 2013
Updating my review (May 2014):
I visit Olive House regularly, and love their many veg options. I get the Mazza platter very often with delicious falafel and couscous. A place I would love to take friends and family where I can get a veg options without any difficulties.