Quantitative approaches to defining and measuring quality in early childhood education and care (ECEC) have provided a key platform for policy development. Yet their strengths and limitations as informants of high-quality ECEC have not been tested. In this study we examine two sources of quantitative data collected over a five-year period for 74 long day care centres: (1) the Early Childhood Environment Rating Scale-Revised and Infant-Toddler Environment Rating Scale instruments which are well-established observational measures; and (2) Australia's nationally administered Quality Improvement and Accreditation System which involves a self-study and validation process. Correspondence over time and across measures was more consistent for the centres identified as providing lower quality ECEC. Variability in ratings of quality was more evident in lower quality centres, whereas high-quality centres showed less variability over time. High quality, however, was less consistently identified across measures. Discussion focuses on the strengths and limitations of these measures of quality, and the implications these have for policy development and future research.