This article describes and analyzes an action research seminar for prospective elementary and secondary teachers. The seminar was a component of a larger study of a science teacher education program whose goal was to graduate teachers who held conceptual change conceptions of teaching science and were disposed to put them into practice. The article addresses the character of the action research seminar, and how it facilitated prospective teachers learning to teach for conceptual change. It does so by outlining the context in which the research was performed and the methods that were used; by summarizing how the action research seminar worked in two successive semesters and the principal themes that were discussed; and presenting the findings with a discussion of their implications for the larger study. There were two major findings. First, the action research seminar helped prospective teachers understand their students' thinking and preferences. More quickly than is usually the case for prospective teachers, they shifted their focus away from themselves as teachers to their students as learners. The process of doing action research, including as it does the gathering of data about student learning, encouraged this shift in focus. Prospective teachers began to probe what their students were thinking. Second, although most of the prospective teachers became practiced in eliciting students' prior knowledge, only a few were able to use their knowledge of their students' thinking to plan their teaching. Various factors hindered the implementation of conceptual change teaching of science. These included the prospective teachers' own (nonconstructivist) views of knowledge, their fragmented and static knowledge about science content, the scarcity of school placements that could model conceptual change teaching, and the conditions of teacher and prospective teacher work.