Adults with serious mental illness and substance use disorders have elevated risk of mortality and higher healthcare costs compared to the general population. As these disparities have been linked to poor management of co-occurring chronic conditions in primary care, the behavioral health setting may be a preferred setting for routine medical screening and treatment. This qualitative study describes early stages of integrating care teams in emerging medical homes based in mental health and addiction treatment settings. Clinicians and staff from ten agencies engaged in the Behavioral Health Home Learning Collaborative participated in qualitative interviews exploring local definitions of "behavioral health home" and initial barriers and facilitators to integration. Facilitators included clear staff roles, flexible scheduling, and interdisciplinary huddles and staff trainings. Challenges included workforce, limited use of electronic health records, and differing professional cultures. Participants advocated for new workflows and payment structures to accommodate scheduling demands and holistic case management.