For students in a perspective English teacher program, enhancing language proficiency and teaching knowledge is essential so that they can participate in the teaching community. This study investigated the acquisition of an unfamiliar discursive practice by four undergraduate students in a perspective EFL teacher training program. The practice is storytelling which is often overlooked in teacher-training programs in the English as a Foreign Language (EFL) context such as in Taiwan. In this study, four undergraduate students in a teacher-training program of a medium-sized university in southern Taiwan were provided an opportunity to tell stories to primary-school children. Qualitative data were collected, including students' teaching experiences and reflective journals throughout the entire project, videotapes of four storytelling rehearsals and the real storytelling episodes, and interviews. By using situated learning as the theoretical framework, this study depicts the change in the students and instructor as well as in the students' co-participation patterns by which the students moved from peripheral to fuller participation. This study provides EFL teacher educators a perspective that considers teacher training as co-constructed development in situated discursive practices.