Research Findings: Early childhood teachers' talk is a key ingredient in children's early language and literacy development, but there has been little systematic synthesis of observational studies that examine relationships between teacher talk and child oral language. In this systematic review of 54 studies, we investigate and synthesize the kinds of teacher language practices and children's oral language outcomes that have been studied to date. We identify four key strands of teacher language practice types: (1) conceptual talk, (2) interactive talk, (3) linguistic features, and (4) management and literal talk, and find that the majority of studies use vocabulary assessments as a proxy for assessing children's oral language development. Next, we apply the idea of language registers, drawn from systemic functional linguistics, to identify the patterns of teacher language practices used for particular purposes, in particular places, and with different participants that were associated with growth in children's oral language development. Practice or Policy: Findings indicate that early childhood teachers can support children's oral language development using strategies tailored to specific settings, including the use of conceptual talk during shared book-reading and the use of elicitations during play and small group settings.