BACKGROUND: Improving quality and patient safety is of increasing strategic importance to health care organizations. However, simply increasing the volume of quality improvement (QI) activity does not necessarily improve patient outcomes. There is a need for greater understanding of QI success factors. PURPOSE: This study looked for differences in QI implementation across hospitals with a range of performance on Patient Safety Indicators. METHODS: We conducted an exploratory comparative case study of 4 Veterans Health Administration hospitals including site visits and interviews with leaders and staff. FINDINGS: Two themes emerged. Project-level QI learning is assessing and modifying specific QI projects relative to expectations. Program-level QI learning is assessing and modifying the overall QI endeavor. The nature of project-level QI learning was similar across sites, whereas we identified qualitative differences across organizations in program-level QI learning. The highest performing organization was evaluating and refining its overall approach to QI, whereas the others were learning how to build and control QI programs. PRACTICE IMPLICATIONS: Program-level QI learning may be key if a QI program is to succeed in improving patient outcomes. This type of organizational learning entails a big-picture, organization-wide view of QI. It also entails second-order organizational learning based on assessment not only of whether QI is being done correctly but also whether the right QI activities are being done, for the right reasons. The organization is "learning to learn." In addition to gaining mastery and control of QI, leaders regularly engage with staff in rethinking QI and experimenting with new approaches. Leaders also assess how QI activity fits in the organization's developmental journey and how it supports realization of strategy.