At large research universities, graduate students are often employed as teaching assistants (TAs) or graduate student instructors (GSIs) to support the educational mission of these institutions. In order to maintain a high quality of teaching, and to provide opportunities for graduate students to grow as teachers, the College of Engineering at the University of Michigan requires all new TAs to participate in a one-day training session prior to the start of the term and a follow-up practice teaching session focusing on active learning teaching methods later in the term. The purpose of this paper is to explore engineering graduate students' perceptions of their teaching experiences, especially their use of active learning teaching methods at a large public research university. This paper investigates how graduate student instructors describe and use 'active learning' in their classes, and identifies potential factors that may contribute to the likelihood that a graduate student instructor will adopt these techniques in their teaching practice. To address these topics, all engineering TAs were invited to participate in an online survey which collected data about their teaching experiences (including terms of teaching and responsibilities), their definition of "active learning," and their use of these teaching methods. The data shows that the majority of respondents value "good teaching" and can articulate how they apply active learning in their classes. Further, the majority apply these approaches at least once per week and believe they are "somewhat successful" or "very successful" with their implementation. Those respondents who did not use active learning were unsure how to use these methods in their specific class, believe that their teaching responsibilities did not allow them to use these approaches, or did not feel as though active learning was necessary. This paper examines these responses further to determine whether or not their teaching responsibilities, their confidence with a variety of teaching-related tasks (e.g., lesson planning, working with students, etc.), and use of teaching peer mentors influence their decisions to incorporate active learning into their teaching practice. Recommendations for faculty supervisors and TA training program organizers are provided.