In this qualitative study, using a socio-constructivist framework, I explored an aspect of learning to teach, describing the process by which a group of preservice teachers construct their understanding of and develop ease with an unfamiliar teaching approach during student teaching. The research design included elements of ethnographic study in that the study involved prolonged contact with the participants.In addition I took a heuristic outlook in that as researcher/supervisor, I also participated actively in the process of learning and in the analysis of what occurred. I both acted as informant about the new teaching approach as well as coach for planning and for activity adjustment after in-class observation. As a result, I was able to highlight those elements of the learning environment and the mechanisms and relationships which contribute to or hinder the learning process. The cooperative learning approach was selected for the study since it seemed to provide an opportunity for varied activities which would respond to different student needs, it is recommended in present School Reform documents and it is not widely used in the high schools in the study area. The participants in the study had to build their knowledge of the approach from scratch for they had not been exposed to cooperative learning during their high school years and their university program barely touched on it. Nonetheless, the participants were able to develop their competence with the approach by using support and ideas from many sources: Their students proved to be the touchstone for their persistence with cooperative learning. Supervisory conversations were occasions for construction of knowledge, for shared reflection and for solution finding. Peers modelled successful activities, shared ideas and problem solved together. The cooperating teachers provided knowledge of their students and management suggestions. Thus the construction process was master-inded by the learner who called upon all available resources to help him build his understanding and bolster his endeavours