The purpose of this study was to examine how oral vocabulary instruction was enacted in kindergarten. Four days (12 hours) of instruction were observed in 55 classrooms in a range of socio-economic status schools. All instruction was coded for evidence of vocabulary instruction for a total of 660 hours of observation. Results revealed that teachers explained word meanings during "teachable moments" in the context of other instruction. Findings revealed one-time, brief word explanations, unsystematic word selection, and minimal time devoted to subject areas, such as science and social studies, in which word explanations were most dense. Teachers serving in economically advantaged schools explained words more often and were more likely to address sophisticated words than teachers serving in economically disadvantaged schools. These results suggest that the current state of instruction may be contributing to rather than ameliorating vocabulary gaps by socioeconomic status.