Children develop rapidly in their early years. A crucial component of this development is a child’s ability to learn and use language. Even before they enter formal education, children have learned much about oral language and literacy through meaningful interactions with others, and from their life experiences. Children, however, do not develop at the same pace – some children arrive in early childhood education and care (ECEC) programs more advanced while others require additional support. Recent reviews of the assessment tools available to ECEC educators show a lack of good quality measurement and a reliance on checklist style inventories or narrative approaches. This paper presents a new measure of oral language and pre-literacy specifically designed to be accurate enough to reliably measure an individual child’s growth. Results from a combined calibration of children’s responses using a many-facets item response model show the measure to be reliable, valid and sensitive enough to measure growth within children and between groups of children over time. Implications for future assessment development and for educators’ practice are discussed, including how such measures can provide insight into what children know, understand, and can do (Reynolds, 2020) and what educators can do to support future learning experiences targeted at children’s specific language and literacy needs.