In this paper, we demonstrate how theory can inform the design of a program to prepare graduate students for faculty careers. Preparing Future Faculty programs within and beyond engineering are not new, but explicit application of Communities of Practice and related literature is novel. We describe a prestigious teaching fellowship program that spans three years of increasing instructional responsibility, and present assessment data to describe the role of faculty mentoring and peer networks in student identity development as a Steward of the Discipline. The results are interpreted in light of the literature, and we conclude with areas for future research.