The National Science Foundation (NSF) in the United States funds Research Experiences for Teachers (RETs) for K-12 science teachers. The RET program seeks to provide science teachers with research experiences so they can provide enhanced science or engineering inquiry experiences for their students. One form of RET that focuses on science pedagogy has resulted in some promising changes in teachers’ thinking and lesson design. This case study examines how a cohort of ten secondary science teachers’ inquiry conceptions and lesson design changed after participating in a science pedagogy RET, and analyzes the relationship between the components of the program and changes seen in teachers’ inquiry conceptions and lessons. Significant changes in teachers’ inquiry conceptions and particularly their lessons were a result of teacher adoption of the inquiry-based instructional modeled during the science pedagogy RET. A theory of action is proposed for RET design that would better promote and support teacher learning and foster changes in classroom instruction.