Previous Extensive Reading (ER) studies almost exclusively focus on English language learners and tend to be limited by their lack of control over how the ER treatment is conducted and assessed. Furthermore, studies that investigate the possible effects of different styles of ER, including Extensive Listening (EL) and Audio-assisted Extensive Reading (AER), are few. The goal of this study was to investigate the possible effects of monitored ER, EL, and AER on the general proficiency development of learners of Japanese as a foreign language (JFL). Using an experimental design, data collection for the first year of this three-year project (currently including data from 92 elementary and intermediate JFL learners) has been completed. First-year results indicate that all treatment groups outperformed the control group, and the AER and ER groups had higher gain scores than the EL group. Pedagogical implications, future directions, and the current impact will be discussed.