Objective: The Routine Opioid Outcome Monitoring (ROOM) tool measures outcomes with opioids using an established framework which includes domains such as pain, mood, opioid use disorder, alcohol use, and constipation. This study aims to validate and establish the test-retest reliability of the computer-administered ROOM tool. Design and Setting: Cross-sectional analysis of an online sample. Subjects: Participants comprised those with chronic noncancer pain who regularly used prescription opioids. Methods: Participants self-completed the online ROOM tool along with other validated measures (validation questionnaire), and those who were agreeable also completed the online test-retest questionnaire approximately two weeks later. Subcomponents of the ROOM tool (i.e., pain, mood, alcohol use, opioid use disorder, and constipation) were validated against longer measures of the same construct using Pearson correlation coefficients. Intraclass correlation coefficients were used to assess the stability of the ROOM tool over time. Results: A total of 324 participants completed the validation questionnaire, of whom 260 also completed the test-retest questionnaire. The opioid use disorder domain showed good sensitivity (73.6) and specificity (75.8) against the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, any opioid use disorder. All ROOM components showed moderate correlation (r ¼ 0.55–0.73) with their longer counterparts. Test-retest reliability was fair (0.58–0.75), indicating that responses were relatively stable over time. Reliability did vary, however, based on the components being measured and how certain tools were scored. Conclusion: The computer-administered ROOM tool is a valid approach for brief monitoring of outcomes with prescribed opioids in primary care settings and appears to be acceptable to people who are using prescribed opioids for chronic pain.