Curriculum materials are crucial tools with which teachers engage students in science as inquiry. In order to use curriculum materials effectively, however, teachers must develop a robust capacity for pedagogical design, or the ability to mobilize a variety of personal and curricular resources to promote student learning. The purpose of this study was to develop a better understanding of the ways in which preservice elementary teachers mobilize and adapt existing science curriculum materials to plan inquiry-oriented science lessons. Using quantitative methods, we investigated preservice teachers' curriculum design decision-making and how their decisions influenced the inquiry orientations of their planned science lessons. Findings indicate that preservice elementary teachers were able to accurately assess how inquiry-based existing curriculum materials are and to adapt them to make them more inquiry-based. However, the inquiry orientations of their planned lessons were in large part determined by how inquiry-oriented curriculum materials they used to plan their lessons were to begin with. These findings have important implications for the design of teacher education experiences that foster preservice elementary teachers' pedagogical design capacities for inquiry, as well as the development of inquiry-based science curriculum materials that support preservice and beginning elementary teachers to engage in effective science teaching practice. (Contains 3 tables, 3 figures and 4 notes.)