What is the role of the teacher in developing learner autonomy? The limited research in this area is seldom situated in theory and often based on self-reported data. This study is situated in sociocultural theory and draws on two constructs, the zone of proximal development and imitation, to explain the teacher's role in developing autonomy. The case of an experienced English as a Foreign Language (EFL) teacher of Japanese college students in an English-language immersion program is examined through 12 lesson observations with field notes collected over a 9-month period, and augmented with 3 audiotaped interviews based on videotapes of the final 3 observations. The interview transcripts were deductively coded for autonomy through control, choice, and responsibility, and these codes used in examining summaries of the observations while looking for patterns of development. The findings show that the teacher understood autonomy as student accountability for their own learning, which he tried to promote by handing over management of classroom activities to the students. One implication is that teacher autonomy was the foundation on which this teacher's cognitions and practices were built. Another is that teachers implicitly know more than they can readily articulate, as the research process pushed the teacher to articulate his cognitions.