Background: The Preschool Speech and Language Program (PSLP) in Ontario, Canada, is a publicly funded intervention service for children from birth to 5 years with communication disorders. It has begun a population-level programme evaluation of children's communicative participation outcomes following therapy. Data are currently being collected for all children who access this service--over 50,000 children each year. Aims: To understand and evaluate how therapeutic interventions in speech-language therapy impact the everyday lives of children and families by applying a theoretical framework. Main Contribution: This discussion paper critically examines how the Bioecological Model of Development can be applied to the study of communicative participation outcomes following speech and language therapy. This model will be used in future analyses of communicative participation outcomes data in Ontario's PSLP. The strengths and challenges of this approach are reviewed.