Professional scientists who pursue a teaching credential bring a great deal of background to students in a classroom, but they may have barriers to the ways they portray the field of science. This study used a multiple-case replication design to determine the role of epistemology in lesson plans of seven scientists becoming teachers. Data sources for this study included: (a) written assignment addressing student scientific epistemology at the beginning of the course, (b) fully-developed written lesson plans for a one-month period, and (c) interviews with participants three months after the course was completed. Two major types of instructional designers, schema-centered teachers and activity-centered teachers, emerged from the data. The schema-centered teachers believed teaching to be a process of developing ideas and approached lesson planning initially from a general perspective and worked to a more specific orientation. The activity centered teachers expressed the need to show students how to think about science rather than allowing students to construct their own conception, and viewed teaching knowledge about the scientific enterprise as an activity to be undertaken only at the beginning of the year.