This study examines the effects of professional development on the content and frequency of university supervisor (n=6) written feedback related to supporting emergent bilinguals in order to improve the quality of observational evaluations provided to elementary and secondary pre-service teachers. Findings reveal supervisors' post-intervention feedback more frequently addressed the needs of language learners and provided a greater breadth of issues related to emergent bilinguals. Interview data reveal key factors explain how the professional development addressed gaps in knowledge and affected confidence levels of university supervisors. Implications highlight the importance of supporting supervisors with targeted professional development opportunities around supporting emergent bilinguals to allow for critical reflection of feedback provided to pre-service teachers.