Background: Oncology outreach is a common strategy for extending cancer care to rural patient populations. Several rural states consistently rely on oncology outreach arrangements and maintain specialized cancer registries to monitor physician travel. However, the nationwide characterization of the traveling oncology workforce is currently lacking, and the extent to which their outreach provides access and minimizes travel burden for rural patients remains unclear. Methods: A 100% fee-for-service sample of Medicare beneficiaries with incident breast, colorectal, and lung cancer from 2016-2018 was used in this cross-sectional study. Oncologists were linked to the patient cohort using Part B professional claims. Traveling oncologists were identified annually by observing hospital service area (HSA) transition patterns and partitioned into travel frequency bins. Encounters associated with a traveling oncologist were considered as “outreach” if they occurred outside of the oncologist’s primary HSA. Hierarchical models were used to examine the separate associations between outreach encounters and log-transformed travel time to first chemotherapy, radiotherapy, and surgery for rural patients. Results: On average, 4,333 of 30,069 oncologists engaged in annual outreach. Of this workforce, 49.5% traveled across HSA borders 1-3 times per year (low), 26.9% 4-12 times per year (medium), and 23.6% >12 times per year (high).The low travel workforce consisted of 52.3% surgeons, 34.2% medical oncologists, and 13.5% radiation oncologists, whereas the high travel workforce consisted of 15.0% surgeons, 52.0% medical oncologists, and 33.0% radiation oncologists. Collectively, traveling oncologists administered 6,677 counts of first radiotherapy, 4,681 counts of first surgery, and 1,623 counts of first chemotherapy for rural patients, of which 22.5%, 16.8%, and 15.0% were completed at outreach locations. In adjusted models, oncology outreach was associated with a 14% reduction (95% CI: 0.82-0.89) in travel time to first radiotherapy and a 13% reduction (95% CI: 0.79-0.95) in travel time to first chemotherapy for rural patients. Conclusions: Our study uses a novel claims-based approach for characterizing the nationwide traveling oncology workforce and supports oncology outreach as an effective means for improving rural access to care. These results provide conservative estimates of the influence of oncology outreach on rural access to care, as our analysis is limited to Medicare beneficiaries and does not consider patients who bypass available outreach services.