Innovative programs and research are needed to address homelessness among youth who have been involved in the child welfare system. Moreover, engagement strategies need to be authentic and relevant to the lived experience of youth who have been involved with multiple service systems. We describe our community-university partnership focused on the development, implementation, and evaluation a comprehensive service model that served young adults (ages 18–24) who were experiencing homelessness and had a child welfare history. The partnership was grounded in positive youth development and developmental evaluation frameworks, and incorporated a participatory research approach to involve peer interviewers as co-researchers in a formative evaluation of the service model. We examine the reasons for incorporating peer interviewers with a “hard to reach” youth population and how the peer interviewer approach was developed and supported through the collaborative partnership. A comparison of longitudinal study response rates before the peer interviewer approach was implemented and a year after implementation showed that 6-month rates increased from 11% to 55% and 12-month response rates increased from 14% to 51%. We discuss lessons learned from this approach to inform future research with youth and young adults and provide methodological insights that can help answer questions about the benefits of involving youth as co-researchers.