Project Summary The co-development of language and executive functions (EFs) in early childhood is a critical part of cognitive development that has implications for a successful transition to school and later academic outcomes. Numerous studies have identified a link between children's language and EFs, both in concurrent and temporal associations (Kuhn et al., 2014; 2016). Moreover, there is emerging evidence that children's language serves as a process mechanism linking caregiver language and children's subsequent EFs (Daneri et al., 2018). These findings have yet to be investigated in childcare environments, where most preschool-aged children in the US spend a significant portion of time. Surprisingly, little is known about how preschool teacher language uniquely supports children's EFs. With nascent research indicating that teacher language supports young children's cognition broadly (Leyva et al., 2015), it is important to establish whether specific aspects of preschool teachers' language is related to children's EFs, and whether child language mediates this association. This knowledge is particularly significant for low- income children, who are more likely to begin formal schooling with lower EFs and this deficit helps to explain the achievement gap (Willoughby, et al., 2015). Using secondary data analysis of two longitudinal datasets, for purposes of replicating findings, we will test if preschool teacher language quality in rural settings prospectively predicts children's EFs directly or indirectly through child language. We will examine if specific types of teacher language differentially predict preschoolers' language and subsequent EFs. Determining the predictive power of specific teacher talk, such as the use of simple or complex language, allows for identification of language practices that can be intervene upon. Analyses will also determine if two measures of teacher language differentially predict child outcomes, contrasting classroom and individual language assessments. Leveraging novel predictors of school-entry EFs, the proposed study highlights the potential for teacher-based language interventions during the preschool years that are beneficial, effective and could be widely implemented.