The present ERP study investigates the neural correlates of pictorial context effects on compositional-semantic processing. We examined whether the incremental processing of questions involving quantifier restriction is modulated by the reliability of pictorial information. Contexts either allowed for an unambiguous meaning evaluation at an early sentential position or were ambiguous with respect to whether a further restrictive cue could trigger later meaning revisions. Attention was either guided towards (Experiment 1) or away from (Experiment 2) the picture–question mapping. In both experiments, negative answers elicited a broadly distributed negativity opposed to affirmative answers as soon as an unambiguous truth evaluation was possible. In the presence of ambiguous context information, the truth evaluation initially remained underspecified, as an early commitment would have resulted in the risk of a semantic reanalysis. The negativity was followed by a late positivity in Experiment 1, but not in Experiment 2, suggesting that attention towards the mismatch affected semantic processing, but only at a later time window. The current results are consistent with the notion that an incremental meaning evaluation is dependent on the reliability of contextual information.