To develop an entry-to-practice quality and safety competency profile for radiation oncology residents to guide training in this area. A list of 1211 potential quality and safety competency items was compiled from a range of international sources, including quality-related course objectives, competency profiles for radiation therapy and medical physics, and other quality-focused organizations such as the World Health Organization and the Canadian Partnership for Quality Radiotherapy. Items that were redundant or beyond scope were eliminated by investigator consensus, generating a refined list of 105 unique potential competency items. This list was subjected to an international 2-round modified Delphi process with experts in radiation oncology, radiation therapy, and medical physics. In the first round, each item was individually scored on a 9-point Likert scale to indicate agreement that an item should be included in the competency profile. Items with a mean score of 7.0-9.0 were included, <4.0 were excluded, and 4.0-6.9 were refined and rescored in Round 2 for inclusion or exclusion in the competency profile following a web-conference discussion. Items ranked for inclusion by >75% of Round 2 participants were included in the final competency profile. Fifteen of the 50 invited experts participated in Round 1: 10 radiation oncologists, 4 radiation therapists, and 1 medical physicist from 13 centers in 5 countries. All 105 items were scored in Round 1, resulting in a mean score of 7.0-9.0 for 80 items, <4.0 for 1 item, and 4.0-6.9 for 24 items (intermediate group). Certain categories emerged as more controversial, for example: change management, equipment quality assurance (QA), and human factors. Web-conference with 5 of the participants resulted in 9 of the 24 intermediate group items edited for content and/or clarity. In round 2, 12 participants rescored all intermediate group items. Ten items were ranked for inclusion by >75% of participants and the remaining 14 items excluded. The final 90 enabling competency items were organized into thematic groups consisting of 18 key competencies under headings adapted from Deming's System of Profound Knowledge, specifically: Appreciation for a System (Process, Standardization & Benchmarking, Organizational & Systems Structure, Accessibility, Risk Management), Knowledge of Variation (Incident Management, Patient QA, Equipment QA), Theory of Knowledge (Change Management, Outcomes), Psychology (Human Factors, Quality Culture), and Safety (Radiation Safety, General/Patient Safety). This quality and safety competency profile may inform minimum training standards for radiation oncology residency programs and assist in CanMEDS2015 implementation. Other relevant professional groups may benefit from the groundwork laid through this process.