This paper focuses on the use of the teaching method Peer-Assisted Reflection (PAR) to help graduate student instructors (GSIs) develop as teachers. PAR engages students in analyzing the work of their peers and providing feedback to promote their abilities of communication, collaboration, and persistence. The goals of the PAR activity were taken as goals for instruction generally, and used to support the GSIs to develop student-centered pedagogies. This report provides in-depth case studies of two of four GSIs involved in implementing PAR in their introductory calculus recitation sections. Two of the GSIs showed considerable changes in practices and beliefs, while the others showed little growth.