Prediction during sentence comprehension is modulated by comprehenders’ relative linguistic ability. To illustrate, in a visual world eye-tracking study, Peters et al. (2018) showed that adult native speakers and childhood L2 learners of English with higher and lower PPVT vocabulary scores were equally successful at pre-activating a likely sentential ending in the presence of supporting context (e.g., pre-activating ‘treasure’ when hearing ‘The pirate hides the treasure’). However, only participants with smaller vocabularies also considered a locally coherent but less-likely (i.e., verb-related) competitor (e.g., ‘bone’ when hearing ‘The pirate hides the treasure’). This suggests that individuals who experience more uncertainty in everyday language interpretation activate less-likely referents. We examined how vocabulary size modulates the variation underlying differences in predictive abilities between native- and second-language speakers. Results showed that participants with higher vocabulary launched a higher proportion of anticipatory fixations to the most-likely continuation (‘treasure’) sooner than participants with lower scores.