This study describes the factors that influenced the ability of four state Medicaid agencies participating in the CHIPRA Quality Demonstration to report the Centers for Medicare & Medicaid Services’ core set of children’s health care quality measures. We draw on 154 interviews, semiannual grant progress reports, and annual public reports. Each state took a different approach to reporting, depending on available technical, organizational, and behavioral inputs. Reporting capacity was influenced by a state’s Medicaid data availability, ability to link to other state data systems, past experience with quality measurement, staff time and technical expertise, and demand for the measures. These factors were enhanced by CHIPRA Quality Demonstration grant funding.