e23107 Background: Adults with cancer often visit the emergency department (ED) during treatment for commonly anticipated issues (e.g. pain, nausea). Some providers have created oncology urgent care clinics (OUCC) to manage these non-emergent issues. Evidence suggests that they are associated with lower ED use. Little is known about the care delivered at OUCCs, and how it compares to ED care. We compared visits from our OUCC to ED visits at our comprehensive cancer center. Methods: We studiedvisits from Jan 1 – June 30, 2023. To limit selection bias, we excluded ED visits if patients were referred by an outpatient clinician, including phone triage. Triage nurses document a validated Emergency Severity Index (ESI, version 4) as part of usual care in the ED, but not the OUCC. The ESI ranks high-severity (level 1 – “patient dying”; 2 – “shouldn’t wait”) to lower-severity (level 5), with the three lower levels distinguished by vital signs and clinical resources needed to stabilize a patient. Two clinicians reviewed OUCC visits and recorded ESIs. We assessed inter-rater reliability of OUCC ESI coding. We used multivariate, mixed-effects methods (visits clustered to patient) to model two outcomes: care escalation (OUCC to ED/inpatient; ED to inpatient) and length of stay (LOS). We excluded visits with ESI at the extremes (1 and 5). We adjusted for sex, age, comorbidities, cancer type and stage, date/time of arrival, and ESI. We then used marginal effects methods to report adjusted outcomes, stratified by ESI. Results: We analyzed 904 OUCC visits (580 patients) and 4,115 ED visits (2,866 patients). Over half (55.5%) of ED arrivals occurred after business hours. Median patient age was 67 (IQR 57 - 74), 48% were female, and 58% non-Hispanic white. Cancer types included 18% hematologic, 17% GI/colorectal, 12% breast, and 7% lung; 11% were advanced-stage. Unweighted inter-rater reliability for ESI was high for a subset of 164 OUCC visits (k = 0.81, 95% CI: 0.72 - 0.89). Although OUCC had a sizable portion of level 2 visits, ED had significantly higher severity. At each ESI level, adjusted rates of care escalation were significantly higher for ED than OUCC (overall aOR 5.6, 95% CI: 4.4 - 7.2), and LOS was longer for ED than OUCC (5.2 hours longer, 95% CI 4.8 – 5.6). Conclusions: The severity of OUCC visits was high, though patient self-referred ED visit severity was higher. OUCC may be more efficient than the ED for managing non-emergency care in this population. Future work should further investigate the quality of care delivered at each site, including cost of care. [Table: see text]