Although there is a recognised need for effective practices to support students on the autism spectrum in mainstream schools, there is a research to practice gap in the area of autism and education, whereby evidence-based intervention may take decades to translate into mainstream classroom practice. Thus, current recommendations are that, rather than presenting mainstream school teachers with interventions developed and tested in clinical or special education settings, a participatory research process should be used to facilitate implementation in real-world mainstream classrooms. This article reports on a case study that aimed to refine a structured teaching intervention package for use in mainstream classrooms, while at the same time tailoring research methods for evaluating the package in these settings. The outcomes of the project are presented with respect to (a) the development and refinement of the intervention package in consultation with a mainstream classroom teacher and (b) the lessons learned during the process that other clinical researchers, teachers, and clinicians could apply when implementing educational interventions in mainstream settings.