Political and community concerns about the quality of teacher education and teacher effectiveness have led the Australian Institute for Teaching and School Leadership to require providers of initial teacher education (ITE) to collect evidence of impact of their pre-service and graduate teachers on learners. Leading teacher educators have expressed concerns about the difficulty of collecting robust, valid evidence of ITE program quality by examining impact of pre-service and graduate teachers on learners, although other jurisdictions and other professions, have moved towards seeking to assess the impact of pre-service and graduate professionals as a measure of professional program quality. Challenges to obtaining robust and valid evidence centre around isolating the impact of pre-service or graduate teachers’ ITE programs from the many situational and contextual factors that can affect learner outcomes. Moreover, the assessment of the impact of pre-service teachers on learning in classroom or other settings occurs when they are in those settings for relatively short periods and often work within parameters established by learners’ regular teachers.The University of Tasmania is taking a research-based approach to determining what evidence of impact of its pre-service and graduate teachers on learning it should collect. We asked: 1. What does literature suggest are indicators of teacher impact on learning?2. What are valid sources of evidence of pre-service and graduate teacher impact on learning that are efficient to collect and analyse? This paper reports on our journey. We conclude that replicable, and high quality impact of pre-service teachers on learners depends on knowledge and skills developed during university-based training and during explicit planning for that learning episode as much as, if not more than, practices applied during that learning episode. We note that evidence informed practice modification is an essential component of pre-service and graduate teachers’ learning and will subsequently influence impact on learners. The paper then discusses our documentary analysis of evidence collected during our courses and provides examples that draw conclusions from interventions and newly-instituted professional experience processes which attempt to capture ‘impact’ in its multi-layered forms. We discuss the efficacy of collecting various types of ‘impact’ evidence, and conclude by suggesting criteria for a set of evidence sources that collectively may start to provide a more robust assessment of the impact of pre-service and graduate teachers from an ITE program on learners.