This mixed-methods study examines how engaging science teachers in a summer Research Experiences for Teachers (RET) followed by an academic-year Professional Learning Community (PLC) focused on translating teacher research experiences to inquiry-based classroom lessons might facilitate changes in their beliefs and classroom practices regarding inquiry-based instruction. Supported with NASA funding, fourteen high school science teachers participated in a large mid-Atlantic university's year-long RET-PLC professional development program. The findings of this empirically-based study suggest that a summer RET program augmented by an academic-year PLC component can help teachers to shift their beliefs from a teacher-centered to a more student-centered approach. However, changes in classroom practices which demonstrate that teachers had transitioned from the use of teacher-centered to reform-centered practices were limited. Moreover, the study's findings have several implications for developers of professional development programs for in-service science teachers and science education researchers.