This study investigates how eight public, centre-based preschool teachers working with low-income children are using different activity settings and content foci to support one aspect of academic language: vocabulary development. Findings indicate that, on average, when teachers engaged children in teacher-led, whole group activities, read-alouds, morning meetings and interactions that focused on science content, they provided a relatively dense vocabulary learning experience. However, there were stark differences between teachers in the amount of support they were providing in these activity settings and content foci -- some teachers were frequently supporting vocabulary learning, whereas others were providing almost no support. In contrast, during informal activity settings, such as free play, transitions and mealtimes, there was very little variability across teachers -- all teachers were providing very little support for vocabulary learning during these activity settings, despite the fact that these activities comprised more than half of observational time. Findings suggest that while some preschool teachers were using certain activity settings and content foci to support vocabulary learning, all teachers in this sample were missing many opportunities to provide support for vocabulary development. Recommendations for early childhood educators and professional development providers are discussed.