Audiobooks allow language learners to read and listen to the same text simultaneously; yet the effects of this bimodal input (written and spoken) on learners' comprehension have been inconsistent, suggesting that the conditions under which audiobooks can help comprehension are not well understood. As such, I explored silent reading speed and text complexity as two potential variables that moderate reading-while-listening (RWL) comprehension. In a within-participant design, 46 English learners in an American university read, listened to, and simultaneously read and listened to two complexity versions of a fictional text. Mixed-effects regression modeling revealed that participants comprehended better in the RWL conditions than in the listening-only conditions, echoing findings from the captions literature. This effect was moderated by neither silent reading speed nor text complexity. There were also no main effects between RWL and reading-only conditions, indicating limitations in the use of audiobooks in language classrooms to promote written text comprehension.