Okay so as of this writing there are:
Veggie Grill (2 locations in OC, including the original flagship store at UCI Marketplace)
Several Loving Hut locations: Orange, Huntington Beach and... Ladera Ranch. Ladera Ranch?
ZPizza with the Daiya cheese option.
Greens Cafe in Irvine.
That vegan Thai place in Irvine that I don't particularly care for (sorry).
Zen Vegetarian, Westminster (some of the mock meats may be non-vegan though)
Bo De, Westminster
Au Lac in Westminster
Thuyen Vien (closed but reopening, hopefully soon).
El Misti Picanteria Arequipe?a - whole vegan menu.
Native Foods, several locations.
There are more, but I have to get back to work. And WHY is IRVINE the steaming epicenter of a lot of this vegan action? Odd, very odd.