Recent events reveal the impact of systemic inequities on marginalized communities and highlight the importance of critical frameworks in science teacher education. Education theorists and research suggest that lack of sociopolitical, or critical, consciousness among teachers limits their ability to engage students in culturally relevant teaching and learning; provoking critical consciousness among white educators is an especially daunting task. Research is needed to uncover how science teacher educators might support the development of critical consciousness among practicing science teachers. In this article, we present findings from a study situated within a larger Design-based Research project to test and revise an instructional sequence grounded in science content, collaborative inquiry, and critical place-based pedagogies. This analysis of how participants' collective awareness developed over the course of a four-day Professional Development workshop offers insight into how innovative in-service science teacher education might be employed to support practitioners' understanding of oppressive systems including those inherent in the discipline of science. Findings suggest that the incorporation of collaborative inquiry as a design heuristic supported teachers' emerging understanding of the role inequitable systems play in disparate health outcomes. In addition, interrogating race and racism in the context of science challenged deficit frameworks and prompted some participants to acknowledge the limitations of their own lived experiences in comparison with those of their students. Implications include a new model for professional development to support practicing teachers' moves toward justice-oriented science teaching and learning.