We investigated task effects on violation ERP responses to Noun-Adjective gender mismatches and lexical/conceptual semantic mismatches in a combined auditory/visual paradigm in French. Participants listened to sentences while viewing pictures of objects. This paradigm was designed to investigate language processing in special populations (e.g., children) who may not be able to read or to provide stable behavioural judgment data. Our main goal was to determine how ERP responses to our target violations might differ depending on whether participants performed a judgment task (Task) versus listening for comprehension (No-Task). Characterizing the influence of the presence versus absence of judgment tasks on violation ERP responses allows us to meaningfully interpret data obtained using this paradigm without a behavioural task and relate them to judgment-based paradigms in the ERP literature. We replicated previously observed ERP patterns for semantic and gender mismatches, and found that the task especially affected the later P600 component.