Current standards emphasize student engagement with inquiry practices. However, implementing inquiry instruction is a formidable challenge for teachers as they often lack models for using and adapting inquiry-based instructional materials. Teacher education programs can provide scaffolded contexts for developing teachers' ability to critique, adapt, and design inquiry-based materials. We describe a qualitative study of 17 preservice teachers enrolled in two consecutive science methods courses. The study characterizes the development of preservice teachers' ability to critique and revise instructional materials. Our findings suggest that teachers improved in their ability to critique lesson plans and to suggest revisions that would make them more inquiry oriented. In particular, the teachers' critiques and revisions increased in sophistication after engaging in instructional design activities during the second methods course.