Action research has been recognized as a useful professional development tool for teaching, but for inservice teachers, conducting action research can be challenging. Their learning about action research can be influenced by social situations--whether in an MA (Master of Arts) program or other professional development. The purpose of this longitudinal case study is to examine how the participants' understandings about action research changed over time in a MA program, the participants' understandings about action research, and the outcomes of doing this research. Various data were collected from semi-structured interviews, informal conversations, e-mail messages, and the participants' final action research paper and follow-up interviews. We discovered both strengths and weaknesses of the program on learning and continuously using action research as teaching tools through the participants' perceptions and consequences of action research. The study concludes with suggestions on how MA inservice teacher education programs can incorporate action research that can be a meaningful professional development tool and develop ways to ensure the quality of research.