When participating in a large-scale, web-based professional development program, to what degree do teachers participate? How useful do they find the program? To what degree do they feel supported in their efforts? What are the associations between participation, evaluation of services, and the level of service teachers receive? MyTeachingPartner provides several levels of support to teachers, and each participant's involvement in the project varies in terms of assigned level, frequency of logging in to the site, and the time she spends on it. This paper compared key data sources, including web navigation logs and teacher survey responses, to describe the relationship between teachers' perceptions of support, their specific project interactions, and the level of service they receive. We explored ways that a large-scale professional development project such as MTP can benefit from identifying and nurturing those elements that best foster teacher perceptions of support.