Read the Labels
Dogs need certain vitamins-specifically B-12-that are not readily available in vegetable proteins, but dogs can, with the proper supplementation, eat a vegetarian diet (that's not to say they can be as healthy with a purely vegetarian diet as they could be with a diet that contains meat, though).
Purchase treats that are made from wholesome fruits and vegetables such as apples, sweet potatoes and carrots. These will contain the highest levels of beta-carotene and other anti-oxidants. Some treats add beneficial ingredients such as grapeseed and flax oil or herbal combinations to address conditions such as anxiety, joint pain or bad breath.
Make Your Own
Homemade vegetarian dog treats can be as simple as serving up a raw carrot or as complicated as steaming, mashing and baking a gourmet biscuit. Avoid grapes, onions, chocolate, macadamia nuts and raisins when preparing homemade snacks. These can be toxic to dogs.