Executive function (EF) encompasses higher-order mental processes necessary for the conscious control of thought and action in the service of goals. Once thought not to apply to children at all, EF is now at the center of a burgeoning body of research on young children over the last 10-15 years indicating that it is a critical foundation of school readiness and performance. Despite the widely agreed relevance of EF to the transition to formal learning, findings have not yet been applied to preschool classrooms in any widespread way. Part of the reason for this is that despite general agreement on the broad definition of EF, the subdomains EF comprises--especially in early life while it is emerging--are still a matter of debate. It is therefore a challenge to bring the relevant concepts down to an even further level of granularity, i.e., specific behaviors ecologically grounded in everyday preschool interactions. We took the initial steps of this challenge by curating EF-related behaviors from the extant literature, expert and master teacher interviews, and observations in high-quality preschool classrooms into a new protocol called Preschool-Setting Executive Function. This observational system includes child behaviors as well as teacher support behaviors that encourage children's organized, higher-order thinking. We then employed the final protocol in an additional set of classrooms to provide an initial assessment of its usefulness in identifying "EF in context." Results indicate (1) EF and EF-support behaviors are low-frequency occurring, (2) children are more engaged in organized thinking than teachers are in the support of it, (3) teachers' presence, especially if they are expanding play, promotes children's real-time EF-behaviors. Results are discussed in terms of how this system may be used as a basis for future professional development to enhance teacher practice around the promotion of EF.