HIV prevention community planning groups were formed to increase stakeholder participation and develop evidence-based comprehensive HIV prevention plans. To date, it is not well understood what factors affect group behavior as the planning group prepares for data-informed decision making. In this observational case study, the authors videotaped 18 meetings of a community planning group (CPG) to observe how a group's behavior changes over time in response to modifications in its structure and function. Discussions on authority and conflict were common, particularly during presentations on prioritized populations and interventions. Changes in the frequency of data-informed discussions were not statistically significant. Observed group conflict may have been an unintended consequence of efforts to improve equity. The authors suggest that formal and informal mechanisms to manage conflict and agreed-on procedures for decision making should be incorporated into the technical assistance offered to CPGs. Future studies should address whether data-informed decisions increase once contentious issues are resolved.