This qualitative case study examined how middle school science teachers conducted collaborative inquiry and reflection about students' conceptual understanding, and how individual teachers in the middle school science group acted and made reflections in response to their collaborative inquiry. It also examined external influences that affected the teachers' ability to engage in collaborative inquiry. Observational, written, and interview data were collected from observations of teachers' face-to-face meetings and reflections, individual interviews, a focus group interview, and online reflections. The results of this study revealed that collaborative inquiry is a form of professional development that includes answering curricular questions through observation, communication, action, and reflection. This approach was developed and implemented by middle school science teachers. The premise of an inquiry is based on a need with students. Middle school science teachers came to consensus about actions to affect students' conceptual understanding, took action as stated, and shared their reflections of the actions taken with consideration to current and upcoming school activities. Activities involved teachers brainstorming and sharing with one another, talking about how the variables were merged into their curriculum, and how they impacted students' conceptual understanding. Teachers valued talking with one another about science content and pedagogy, but did find the inquiry portion of the approach to require more development. The greatest challenge to conducting collaborative inquiry and reflection was embedding teacher inquiry within a prescribed inquiry that was already being conducted by the Sundown School District. Collaborative inquiry should be structured so that it meets the needs of teachers in order to attend to the needs of students. A conducive atmosphere for collaborative inquiry and reflection is one in which administrators make the process mandatory and facilitate the process by removing an existing inquiry.