This study represents a first iteration in the design process of the Growing Awareness Inventory (GAIn), a structured observation protocol for building the awareness of preservice teachers (PSTs) for resources in mathematics and science classrooms that can be used for culturally responsive pedagogy (CRP). The GAIn is designed to develop awareness of: how students use language in classrooms; relationships between teacher questioning patterns and student participation; messages conveyed by the classroom environment; and ways to incorporate students' interests into lesson plans. The methodology took the form of a multiple case study design with fourteen mathematics PSTs as one case and five science PSTs as the other case. The participants' response to the GAIn and lesson plans served as data sources. Findings reveal that the GAIn scaffolded PSTs' awareness of their students, their own attitudes, and several elements of CRP. However, there were key areas of CRP that were neither explored with the GAIn nor identified by the participants. Consistent with design-based research, outcomes include a design framework for revision of the GAIn and a theory of action that situates it within a teacher education course that includes a field placement.