Evaluation, Ahead of Print.
Theory-based evaluation has undergone changes over time, adapting to challenges and aligning with trends that emphasise increased participation and complexity. However, integrating both high participation and complexity in programme theory does not consistently led to productive outcomes in intricate systems. This article introduces contingency-oriented questions to assess the appropriate balance of complexity and participation in theory-based evaluation. Using a case study focused on the Accelerating Achievement for Adolescents Hub, a Global Challenges Research Fund initiative, we demonstrate the practical application of these questions. Our analysis highlights why efforts to elaborate a more complex programme theory were unsuccessful and explains the rationale behind concluding the project with a theory characterised by more moderate complexity and participation.