INTRODUCTION: The Northwestern Medicine Breast Cancer Quality Improvement Collaborative (NM BCQIC) is a novel, multidisciplinary cancer-focused quality collaborative of diverse hospitals in a large health system. NM BCQIC undertakes collaborative-wide QI projects to improve adherence to best practice guidelines, which are carried out by local cancer QI teams with support and guidance from the collaborative coordinating center. The effectiveness of participation in mentored QI collaborative such as NM BCQIC in improving QI aptitude is unknown. Thus, our objective was to evaluate changes in QI aptitude amongst oncology providers participating in NM BCQIC. METHODS: Cancer QI teams of oncology providers at each hospital participated in a multifaceted intervention, which included a QI curriculum consisting of online modules, in-person training, recurring meetings with coaches, and webinars, all centered around implementation of a collaborative-wide QI project to improve NCCN guideline-based genetic counseling referrals for breast cancer patients. An oncology-focused adaptation of the QI Knowledge Application Tool (QI-KAT), a validated QI assessment, was administered pre- and post-intervention. Three educators scored each de-identified exam utilizing a rubric-based scoring tool (max. score: 50 points; “QI expert-level” score >80%). Scoring discrepancies were discussed until consensus was achieved. Changes in mean scores were assessed using t-tests; differences in scores across hospitals were assessed using ANOVA. RESULTS: Across the 5 participating NM BCQIC hospitals, 17 pre-intervention and 12 post-intervention QI-KATs were collected. Overall, mean scores significantly increased from 67% (SD 18.1%) to 81% (SD 9.0%, p<0.01). Individual scores ranged from 32-96% on the pre-test to 60-94% on the post-test. QI expert-level scores (>80%) were achieved by 29% of participants pre-intervention and 75% post-intervention. All hospitals demonstrated improvement in mean test scores, with absolute percent increase in test scores ranging from 11.6% to 23.2%. CONCLUSION: Despite varying baseline QI experience among oncology providers, participation in NM BCQIC’s multifaceted intervention led to significantly improved QI aptitude amongst a wide range of providers. Formalized education combined with practical QI experience (i.e., QI project participation) may be beneficial in equipping providers with expertise and tools to successfully execute QI in cancer care.