Research shows that building teacher expertise can be enhanced through collaboration among colleagues, potentially through communities of practice (CoP) and professional learning communities. However, much of this research primarily investigates student and teacher outcomes. Therefore, our collaborative case study explored the critical aspects of the process behind forming a multimembership CoP consisting of high school teachers from two different schools: one school in the Southeast and one school in the Southwest U.S. We wanted to understand their successes and challenges as they navigated the beginning stages of their work together. As noted in current research, this process was complicated; however, teachers noted success and challenges regarding collaboration, time, and communication. Notably, ample time was required to develop relationships and trust before participants could openly share their thinking and demonstrate a willingness to shift their perspectives about instructional planning. While more research is needed, our findings share initial teacher-reported information about moving past the potential power imbalance between CoP teams and navigating the ebbs and flows of the early stages of partnerships.