Elementary science education calls on teachers to facilitate student learning of the content of science while they engage in the work of scientists. Additionally, recent national and state standards incorporate the practices of engineering into science education throughout grades K-12. However, many practicing teachers receive little to no professional development related to this shift in educational practice for the science classroom. To exasperate the issue, elementary teachers are generalists by nature without content or practical expertise in science and engineering content or practices. This study investigated how two fifth-grade teachers experienced co-facilitating an independent engineering fair with their students. The findings from this study can inform the ways in which teacher educators can support the incorporation of authentic engineering practice in the elementary classroom.