In this paper, we describe our approach to mentoring Graduate Teaching Assistants (GTAs) as teaching and learning protégés within the context of a challenging undergraduate honours thesis course. An approach to mentoring GTAs in this multifaceted course is outlined, while providing practical strategies that expose GTAs to various aspects of the teaching process so that they become co-educators. Reflections from two GTAs that highlight the benefits and challenges of the co-educator model are also presented. Evidence from course evaluations provide support for the critical role that GTAs engaged as protégés play to enhance student success in this academically rigorous capstone course. We argue that mentoring GTAs for teaching development by treating them as co-educators can be rewarding, improve course outcomes, and enhance the student experience. [Articles in this journal were presented at the University of Calgary Conference on Postsecondary Learning and Teaching.]