Active learning has been a curriculum mandate in the Indonesian education system since the 1980s. Nonetheless, practical gaps existed, as evidenced by the dominance of teacher-centered instruction in public schools. The field needs research depicting how active learning works and enhances learning. Thus, we conducted a qualitative case study focusing on one method within active learning pedagogies: cooperative learning. Specifically, we examined how one of its techniques, i.e., Jigsaw, operated and optimized English as a foreign language (EFL) learners' reading comprehension. We involved one EFL teacher and her students in eighth grade. Data were gathered through classroom observations, in-depth interviews, and analysis of instructional documents. Our data analysis revealed some missed steps in the teacher participants' lesson plans, specifically in the main learning activities sections that had the Jigsaw procedures. However, these activities were enacted in the actual classroom use. The teacher participant also modified her lessons to make Jigsaw more effective. Additionally, she tackled challenges that occurred during the process, especially in dealing with low levels of reading comprehension, unmotivated students, and limited time. For effective use of Jigsaw and considerations when making adjustments in classroom practice, we recommend that teachers understand cooperative learning principles and how they manifest in the procedures of the selected technique(s).