A variety of patients - including women, older, racial/ethnic minority, rural, homeless, and justice-involved patients - are vulnerable to experiencing poor healthcare access and quality, such as lower quality substance use disorder treatment, than other populations. The current study examined receipt of medications for opioid use disorder by vulnerable populations within Veterans Health Administration (VHA) facilities to determine whether there are patient and facility factors that are associated with disparities in care. Using national VHA clinical/administrative data from Fiscal Year 2017, we calculated receipt of medications for opioid use disorder using the American Society for Addiction Medicine quality measure specifications. A mixed-effects logistic regression model tested whether patient vulnerability (ie, women, older age, racial/ethnic minority, rural residence, homeless, and justice-involved) and facility (eg, regional location, availability of a methadone clinic) characteristics were associated with medication receipt. Among the 53,568 veterans at VHA facilities diagnosed with opioid use disorder in Fiscal Year 2017, vulnerable populations - including women, older, Black, rural, homeless, and justice-involved veterans - had lower odds of receiving medications for opioid use disorder than their nonvulnerable counterparts. Veterans had higher odds of receiving medications at facilities with a higher proportion of patients with opioid use disorder, but lower odds of receiving medications at facilities in the Southern region compared to the Northeast region of the United States. Quality improvement efforts targeted at vulnerable populations are needed at the VHA to ensure these groups receive the same quality of substance use disorder treatment as other veterans.