Humans can integrate information from a rapidly changing speech stream with astonishing speed. In this study, we measure the impact of vocabulary knowledge on the incremental integration of speech using language-mediated anticipatory eye-movements. Following Kamide, Altmann & Haywood (2003), Experiment 2, we examined the degree to which an upcoming sentential Theme is anticipated by a combination of information from an Agent and Verb (eg. The pirate hides the treasure vs. The dog hides the bones). Replicating prior results, combinatory effects of the Agent and Verb yielded anticipatory looks to the Theme. When participants performance was split by receptive vocabulary score, differences in anticipatory eye movements were apparent. The group with higher vocabulary scores was faster to integrate Agent and Verb information to correctly look at the upcoming Theme. Together our findings are suggest that prior language knowledge plays a pivotal role in even simple sentence processing tasks.