This study conducted a one-year experiment to investigate whether process-centered drama-based or improvised dramatic approach (IDA) enhances learners’ oral competence in large EFL conversation class in Taiwan. The actual language growth of (control-group) learners who have stopped receiving such teaching approaches and were treated with more traditional teaching approaches instead were also investigated. The study began by examining learners’ initial level of oral English competence at the beginning of the one-year conversation course, it then applied the present study’s teaching approaches to both groups of learners during the first half period of the study. Halfway through the study, while test-group learners still received the present study’s teaching approach, a more traditional English teaching approach was applied to control-group learners. At the end of the research, it examined the differences in the teaching/learning effect of both groups of learners by again comparing their current level of oral English competence, to see whether the present study’s teaching approach was actually facilitating English teaching/learning. The findings suggest that IDA does have a positive influence on the enhancement of students’ oral English learning outcomes.