Under your My Active Tours > View & Manage Tour > Traveler Profiles > Dietary Preferences
Here you can specify if you want Vegetarian or Vegan meals, that is if you have dietary restrictions and you haven't done so during the tour signing up process.
I'm a pescatarian and it's not listed as an option; I simply select 'vegetarian' in my tour booking and let the tour guide know on day 1 that I also eat fish. All the tour guides in my previous tours would arrange either vegetarian or fish meal for my entrée. The side dishes shared by the table usually are a combination of vegetarian and omnivore, so I just eat those I can eat.
P.S. Breakfast is always buffet style and comes with a combination of vegetarian and meats.