This study investigated the application of an online videocase discussion community into fostering preservice and inservice EFL (English as a foreign language) teachers' professional development in Taiwan. This investigation further revealed the nature and development of discussion discourse and the participating teachers' perceptions of this online learning experience. Also included were potential concerns or difficulties encountered by these community members. There were 21 preservice teachers, 7 secondary school teachers, and 4 university teachers involved in this study. Multiple data collection methods included teaching videos, online discussion messages, interviews, reflection journals, and an open-ended questionnaire. The findings showed that the preservice and inservice teachers appeared to respectively play different roles in discussing teaching videocases online. Yet, what they noticed in the teaching events shifted from diverse to similar focuses after engaging in online videocase discussion for almost one year. These teachers further perceived professional learning opportunities in this community, albeit several issues might hinder some of them from joining the discussion frequently. Pedagogical implications and research suggestions are offered for teacher educators and researchers to further codify and document teacher professional development in various online videocase discussion contexts. (Contains 4 figures and 5 tables.)