Teachers use curriculum materials as a guide in their planning, critiquing and adapting them to address reform-based goals and practices and specific contextual needs. To become well-started beginners in planning lessons, novice teachers need opportunities to develop their pedagogical design capacity—that is, their ability to use personal and curricular resources in designing instruction for students. This study investigated the use of reform-based criteria in supporting 24 preservice teachers enrolled in an elementary science methods course. In learning about and applying criteria, the preservice teachers developed aspects of their pedagogical design capacity by expanding their analysis ideas and refining their knowledge and beliefs about curriculum design. However, many struggled with analyzing lesson plans in a reform-oriented way during student teaching. This occurred, in part, because the preservice teachers navigated different settings that conveyed conflicting ideas about the reasons why teachers make modifications. The methods course emphasized the importance of modifying materials to promote reform-based science teaching, but few preservice teachers observed their mentor teachers make adaptations for this reason. These findings have important implications for theoretical models on curriculum materials use and the design of science teacher education.