- Canadian radiation oncology (RO) residency programs transitioned to a competency-based medical education (CBME) training model named Competence by Design (CBD) in July 2019. Prior to this, CBD was piloted in a single RO training program to characterize assessment completion and challenges of implementation. Six residents and seven staff participated in a mixed-methods study and were oriented to CBD. Four Entrustable Professional Activities were assessed over a 4-week-long block and documented using online assessment forms. Anonymized assessments were analyzed to characterize completion. Post-pilot surveys were completed by 4/6 residents and 5/7 staff. Semi-structured post-pilot focus groups were conducted with all residents. Assessments were requested and documented on a weekly basis. Narrative comments were found in 68.1% of assessments, of which 26.7% described specific examples of observed competence or recommendations for improvement. Three of five staff believed that assessments have a negative impact on clinical workflow. Three themes were identified: (1) direct observation is the most challenging aspect of CBD to implement; (2) feedback content can be improved; and (3) staff attitude, clinical workflow, and inaccessibility of assessment forms are the primary barriers to completing assessments. This study demonstrates that CBD assessments can be completed regularly in an outpatient radiation oncology setting and that implementation challenges include improving feedback quality, promoting direct observation, and continuing faculty development to improve perceptions of this assessment model. Further study is required to identify best practices and expectations for the discipline in the era of CBME.