This study focuses on the development of a reliable coding scheme (CP-CODER) for studying interaction dynamics during the co-production of a public service involving priority communities. CP-CODER addresses the need to involve priority populations in the development of public services, an approach that has been recognized as difficult because of the high possibility of their experiencing negative health, social, and economic outcomes. The coding scheme was designed to capture group dynamics and forms of public engagement by adopting and integrating existing theoretical frameworks in the public service management and qualitative method literature. Coding was conducted on the transcripts of four co-production workshops, which included 26 family caregivers, three local health and social care service provider representatives, and five researchers involved in the co-production of new community-based services. One category was added to the two theoretical frameworks. The kappa ranged from 0.70–1.00 for the eight variables and the 26 individual items. The overall kappa was 0.91, while the overall percentage of agreement was 91.16%. The results of the pilot test showed the importance of integrating and managing three dimensions in co-producing with a priority population: the turn-taking, the content, and the level of abstraction of the discussion. The findings of this study have enhanced and supported both practitioners and researchers in co-producing services, ensuring the equal contribution of all participants, even those whose voices are rarely heard.