["Health Expectations, Volume 29, Issue 2, April 2026. ", "\nABSTRACT\n\nIntroduction\nCo‐creation processes are part of a movement to create change in collaboration with people with lived and living experience (PWLLE); in this paper we focus on experience with health and social services. Research co‐creation with PWLLE is increasing, however, processes tend to include people who are well connected in health and research environments, often excluding equity‐deserving groups (EDGs) who experience barriers to engagement in research and society more broadly (e.g., people with mental health conditions, immigrants, refugees, people who are unhoused).\n\n\nMethods\nWe conducted an evaluation to understand how equity‐based co‐creation (EqCC) is enacted in health and social services and what outcomes are produced. Informed by realist evaluation methods, we used multiple case study methodology to explore and describe how co‐creation was enacted in four sites that were actively conducting EqCC projects. The case study sites were engaging in projects on student mental health and well‐being; youth mental health transitions; individuals in critical care; and women experiencing complex long‐lasting homelessness. A variety of data sources were collected including interviews with 2‐3 key members of each project, organisational documents (e.g., meeting minutes, ethics approvals, reports), and observations. Data analysis included identifying the contexts, mechanisms, and outcomes, and causal configurations to develop a deductive coding scheme and codebook.\n\n\nResults\nThe causal configurations were found to be consistent with the data collected at the four sites: (1) Values (the culture and values that enable co‐creation); (2) Driving Issue (a community‐identified problem as the catalyst for the co‐creation to occur); (3) Organisational Infrastructure (the organisation's tangible infrastructure to support long‐term co‐creation, including funding, time, and training among others); and (4) Experiential Knowledge Network (people involved in the co‐creation, including the networks and partnerships created prior to, during, and as a result of the co‐creation).\n\n\nConclusions\nThe causal configurations explored in this evaluation identify the key contexts, mechanisms and outcomes that support co‐creation with people from EDGs. These may inform inclusive co‐creation project design and the development of a middle range theory of equity‐based co‐creation.\n\n\nPatient or Public Contribution\nThis research was co‐designed and co‐produced by researchers and PWLLE who were members of the McMaster University Co‐Design Hub at the time of the project. The research questions guiding this work were informed through ongoing conversations with members of different communities affiliated with the McMaster University Co‐Design Hub. Co‐author LML identifies as a PWLLE and was instrumental in developing the research question, writing and discussing the causal configurations, and contextualising findings. We shared project updates at numerous team meetings (which included researchers and PWLLE) over the course of the research. Insights and feedback were sought at these meetings which helped to contextualise the work and understand the topic from multiple lenses, including PWLLE.\n"]