Default options have a powerful effect on a broad range of decisions. We examine the degree to which default options can increase the consumption of healthy items as an add-on to a regular entrée. We run an experiment in a college cafeteria in which we vary whether hamburgers are served automatically with tomatoes or whether the tomatoes have to be added by the customer. We find that including tomatoes by default more than doubles the fraction of customers eating a tomato with their hamburger (74% vs. 30%). We also use observational data from six restaurants that serve hamburgers and find that including a tomato by default significantly increases consumption of tomatoes. These results demonstrate that default options can work to improve healthy eating decisions.