The aims are 1) to develop and refine all manuals and protocols for Cornerstone, 2) to determine the feasibility, acceptability, and preliminary impact of 'Cornerstone' relative to treatment as usual (TAU) on mediating outcomes (e.g., stigma), service use, and improved mental health and functioning outcomes, and 3) to explore implementation of Cornerstone through individual and group interviews with key stakeholder partners on aspects of the transforming local, state and national service context (e.g., staffing, payment). As a multidisciplinary team of professionals on the local, state, and national level we are committed to bridging the science to service gap for youth transitioning to adulthood with mental health challenges. Using qualitative methods and an RCT, this study is the first to examine a true transition intervention. We believe mental health services research that focuses on the transition to adulthood with innovative service delivery strategies that span developmental silos will decrease the number of TAYMD with unmet mental health needs.