The multiyear study discussed in this paper focuses on the use of a course management system (CMS) to deliver video clips and interactive mathematics investigations and to support shared reflections in a field-based elementary mathematics methods course. The findings reveal that virtual observations of mathematics teaching episodes in diverse classrooms and participation in interactive mathematics activities and shared reflections via the CMS online discussion board challenged the preservice teachers to reconstruct their beliefs about mathematics teaching and diverse students. Classroom observations and excerpts from the discussion board illustrate how the CMS promoted changes in the preservice teachers' mathematics knowledge and instructional practices. This study gives rise to important findings on the relationships between shared online reflections on virtual observations of mathematics lessons and mathematics teaching in diverse classrooms that are being utilized to inform decisions about teacher preparation programs and the mathematical education of diverse student populations.