This article presents the findings of an impact study of a short teacher training course in teaching English to speakers of other languages (TESOL). Impact is conceptualised as teacher learning, particularly perceived achievements in learning, evidenced in the ways teachers talk about their work in TESOL. The theoretical framework for the research draws on sociocultural theories of learning, particularly situated learning theory and identity formation within communities of practice. In making these links and relating them to a specific programme for teachers in TESOL, this article furthers understanding of how teachers learn in a preservice course in ways which translate to readiness for work. The analysis of interview data from 27 novice teachers in their first months at work reflects a positive and intense learning experience on the course, which establishes both confidence and a clear idea of what the TESOL task involves. The authors relate these findings in the data to the construct of "furnished imagination": the combination of knowledge, procedural awareness and skills, dispositions, and identity which the teachers take from the course as the conceptual toolkit for work in TESOL. The imagination is furnished through the intense, iterated cycles of input, observation, performance, and feedback as well as through interactions with admired teacher educators. (Contains 2 tables and 5 footnotes.)