Unfortunately, there aren't too many Hollywood fictional characters who are as loudly vegetarian as Mr. Spock. Actually, he was originally slated to not eat at all but, fortunately for us, this was soon changed, instead making him prefer fruits and vegetables (over slain animals). This is made clear in several Star Trek episodes.
In fact, T'Pol, another Vulcan, posits that only unenlightened races "consume the flesh of animals." And to establish the fact that fruits and vegetables are available on the enterprise, we are told that there is a hydroponic greenhouse; we are also constantly reminded that the ship's resequencers and replicators can produce just about any kind of food (including, we assume, nutritious, natural ones).
To further elaborate on Spock's commitment to the vegan lifestyle, we see him strongly chastising himself for eating animal fat in the "All Our Yesterdays" episode, while he and Dr. McCoy are stranded on a prehistoric ice era planet. Then again, this episode reminds us that Mr. Spock is, after all, part human; not only is he eating flesh but also falling for a beautiful woman, in spite of his ability to supposedly suppress wild emotions.
What Exactly Do Vulcans Eat? Read On to Page 3