A lack of reading quantity in EFL (English as a Foreign Language) classrooms has remained one of the most serious problems faced by teachers of English in Japan. Although the extensive reading (ER) approach is regarded as having significant potential in addressing this problem, it is not used in many EFL classrooms. This study investigates the effect of a quasi-extensive reading program on Japanese high school EFL learners' reading comprehension, reading speed, and their perceptions of the program. The participants in the treatment group were 96 high school students who engaged in a reading activity with teacher-made materials for the first five to ten minutes of class for approximately five months. Some of these students also read graded readers outside of class. Progress in reading comprehension and speed was measured against a parallel control group that received no treatment in a pre- and post-test format. Results revealed that the treatment group, especially those who read graded readers, scored significantly higher in reading speed and comprehension than the control group. The findings suggest that Japanese high schools and more broadly, English teachers in input-poor EFL settings should increase reading input within the students' linguistic levels both inside and outside of the classroom.