Peer assessment (PA) has transformed traditional teacher-only assessment into the student-centred assessment. While this pedagogical approach has been adopted online in recent years, incorporating PA into classrooms has proven to be challenging. In this study, mobile-supported PA (M-PA) activities using Instant Response System (IRS) mechanisms to enhance oral proficiency are proposed for English as a Foreign Language (EFL) students. A quasi-experiment was conducted to evaluate the effectiveness of this approach in the context of an English language course at a university. A total of 60 university students participated, 30 of whom were in the experimental group using the M-PA method and 30 of whom were in the control group using the conventional teacher-only assessment method. The results show that the M-PA method can effectively promote students' oral proficiency, facilitate personal reflection, and foster positive perceptions of learning.