The study aims to investigate the effect of post-reading question-generation activities on Korean middle school students' English reading abilities with respect to cooperative learning. Two groups of students read the same reading materials; however, one group as an experimental group generated questions of three types, literal, inferential, and evaluative questions, while the other group as a control group answered comprehension questions. Each group was further divided into two sub-groups by cooperative and individual learning. A statistical analysis of the recall test scores reveals a positive effect of post-reading question-generation activities and cooperative learning on English reading abilities. The reading test scores by the three question types further illustrated variations across the question types: the experimental group outperformed the control group in the inferential and evaluative questions and individual learning was detected to be more effective than cooperative learning in the evaluative questions. Interactional effects were observed between post-reading activities and cooperative learning in the literal and evaluative questions. The findings suggest question-generation activities as a beneficial post-reading task, though their effectiveness can vary by question types and learning context.