This study expands on previous research into filler-gap dependency processing in second language (L2) English, by means of a replication of Canales's (2012) self-paced reading study. Canales, among others, found that advanced L2-English speakers exhibited the same processing behavior that Stowe (1986) found for native English processing: On encountering a filler, they posited gaps in licensed positions and avoided positing gaps in grammatically unlicensed island positions. However, the previous L2 studies focused on advanced-level L2 proficiency and did not test specifically for first language (L1) influence. The present study compares two groups of intermediate-level L2-English speakers with contrasting non-wh-movement L1s, Jordanian Arabic and Mandarin, to investigate the effects of L1 influence and individual differences in proficiency. Our results provide evidence that at intermediate level, too, L2 filler-gap processing adheres to grammatical constraints. L1 did not affect this behavior, but proficiency effects emerged, with larger licensed filled-gap effects at higher proficiency.