The next generation of professors will come from today's graduate students and post-doctoral fellows, but we do not know much about their preparation to use research-validated teaching practices. This study characterizes the teaching beliefs of graduate students and post-doctoral fellows who represent future geoscience instructors though we believe the implications go well beyond one discipline. We analyzed results from more than 600 participants who completed the Beliefs about Reformed Teaching and Learning (BARSTL) survey and a subpopulation of sixty participants who responded to the Teacher Belief Interview (TBI). We compared teaching beliefs on the basis of several factors including gender, teaching assistant experiences, and participation in professional development.