In two visual-world eye-tracking experiments, we explore the extent to which conflicting first-language (L1) based grammatical parses influence second-language (L2) learners' on-line and off-line interpretation of sentences in the L2. We used cross-linguistic structural priming to potentially boost competition from the L1 grammar during the processing of wh-questions in English. For L1-German learners (Experiment 1), sentence-final interpretations showed effects of conflicting L1 parses in the greater number of misinterpretations of English subject as object wh-questions than vice versa. In a follow-up experiment with a comparison group of L1-Japanese learners (Experiment 2), we found the reverse pattern in sentence-final interpretations, with lower accuracy on English object than subject wh-questions. The asymmetry in comprehension accuracy between Experiments 1 and 2 demonstrated that the effect observed among L1-German learners reflected grammar competition from the L1 rather than general L2 effects. In both experiments, we observed cross-linguistic priming from L1 object questions to L2 object questions in on-line processing. Yet, cross-linguistic priming did not enhance competition from L1 object questions on L2 subject questions in Experiment 1 as reflected in comprehension accuracy or eye-gaze during processing. Together, these findings present evidence of cross-linguistic structural priming for equivalent interpretations (object-object), but indicate that priming does not extend to competing L1 interpretations of word-order equivalent structures cross-linguistically (object-subject). We suggest that interference from conflicting L1-based grammatical parses is narrowly delimited in intermediate to advanced L2 sentence processing.