Is Potbelly Broccoli Cheddar Soup Vegetarian? Potbellys Broccoli Cheddar Soup is creamy and tasty. But is it vegetarian? That depends on the ingredients. Many restaurant versions of cheddar soup use chicken broth for more flavor. It has broccoli, cheddar cheese, and a rich base. This means the soup may not be strictly vegetarian. For sure, check with Potbelly or look at their official allergen and ingredient list before you order.