The Quality Initiatives Research and Evaluation Consortium (INQUIRE) Data Work Group was convened to address a request from stakeholders for information on building an effective data infrastructure to support activities including monitoring, continuous program improvement, reporting, validation and evaluation in Quality Rating and Improvement Systems (QRIS) and other quality initiatives. The INQUIRE Data Toolkit was designed to provide tools to support effective data collection and the use of data to answer important policy and reporting questions through the use of common data elements. (author abstract)