This multi-methods investigation was conducted to examine the experiences of preservice and in-service elementary teachers (n=11) from rural and American Indian Reservation communities who participated in an NSF-funded Research Experience for Teachers (RET), a summer residential research-focused professional development experience. The primary intent of the professional development was to build elementary teachers' self-efficacy in the design and implementation of community-centered and culturally responsive engineering education curricula. Over six weeks, teachers participated in energy-related research experiences in campus engineering laboratories while simultaneously developing engineering curricula for their elementary classrooms that focused on energy, a cross-cutting elementary topic. Results indicate that teachers showed significant gains in personal teaching efficacy beliefs in science and engineering. Findings also suggest that participating teachers felt significantly more comfortable teaching engineering post-program compared to pre-program. Quantitative results from this study align with the qualitative findings and indicate that the experience positively impacted teachers' capacities to teach engineering and integrate culturally responsive practices. Results also help identify specific attributes of the experience that contributed to their professional learning. Findings from this study contribute to the refinement of theories on teacher self-efficacy in engineering education and help guide future professional development efforts that foster inclusive student engineering identity formation within their classrooms.