The California Department of Health Care Services awarded the Orange County Health Care Agency (HCA) a Homeless Mentally Ill Outreach and Treatment (HMIOT) grant in late 2018. The HCA partnered with Telecare to create intensive outreach and mobile mental health treatment components within its existing Full Service Partnership (FSP) contract funded through the Mental Health Services Act. The goal was to increase access to behavioral and mental health services and housing for people with serious mental illness who were also experiencing homelessness and had not been engaged in services. The HCA and Telecare began offering services in April 2019, with outreach efforts continuing through November 2021 and treatment services continuing through December 2021. Starting in March 2020, the Urban Institute conducted a year-long assessment of the implementation and outcomes of the HMIOT services. This report describes those services and outlines the assessment’s methodology and findings.