Structural change approaches, also called policy, systems, and environmental change approaches, have been increasingly promoted and adopted by public health agencies in the past decade. These interventions require attention to multilevel, complex and contextual influences on individual and community health outcomes, requiring a sound theoretical framework that links the many processes and outcomes over time. The Model Communities program of Cook County, Illinois Communities Putting Prevention to Work program employed a theory of change (ToC) framework to inform the evaluations' design and execution. The main objective of this study was to apply findings from the longitudinal multiple case study evaluation to develop an adapted ToC. We conducted 97 key informant interviews across three waves, with a focus on Model Communities program participants', Communities Putting Prevention to Work staff, and technical assistance providers' experiences over time. Four analysts organized and coded the data using qualitative software; exploratory functions and data matrices were employed throughout three waves of analysis. Adaptations to the ToC included the addition of a construct, "change readiness," as well as refinements to constructs: organizational capacity (human capital, technical assistance, informal and formal leadership), local partnerships, and the importance of sustainability. The findings offer a data-informed theoretical framework that may be considered for use in evaluations of structural change interventions in complex and diverse counties.