Graduate students in STEM fields undertook a 9-month training program focusing on practice-based development of active teaching methods. As instructors of record in their own senior-level courses, these trainees were observed on their independently designed classroom sessions using the COPUS classroom observation tool. Compared to a large sample of college STEM instructors, trainee instructors in this program showed more interactive teaching at this early part of their careers. Through their use of a range of active methods, this study suggests that trainees from this practice-based program will begin work in the teaching profession in strong position to maximize outcomes for their students.