Given the fact that the large class phenomenon cannot easily be eliminated, it is important for teachers to develop effective strategies to teach English in large classes. The purpose of this study was to understand in what ways post-observation discussions lead to increased self-awareness of a college English teacher concerning pedagogy with special reference to large class teaching. Data were collected from document analysis, observations, and discussions. The post-observation discussions were structured using the theoretical frameworks of the Cooperative Development model and the Collaborative Conversation Approach. Data analysis generated four themes: Student participation, affective factors, classroom management, and instructional strategies. This study provided insights which might be useful to teachers who teach large classes in China and around the world. It also provided implications and recommendations for further research.