Research literature has long indicated that action research may stimulate practitioners themselves to actively evaluate the quality of their practice. This study is designed to report the use of action research for the development of early years professional practice by analyzing the pre-project and the post-project video-filmed teaching events. The finding was that action research might support knowledge development in the teacher profession. However, the teacher's ability to accommodate outside knowledge might be limited by one's inside knowledge. The study helps to clarify the assumptions and potentials of action research for teachers learning to teach.