While the past few decades have witnessed enormous growth in research on web-based peer assessment in second and foreign language (L2) writing, little attention has been paid to student engagement with online peer assessment, especially their behavioral engagement. This behavioral engagement captured the pre-service teachers’ revision operation and revision strategies after receiving web-based peer assessment. We explored how 4 university EFL pre-service teachers behaviorally engaged in web-based peer assessment on L2 writing. We collected multiple data sources: observation, online interviews, and stimulated recalls. Findings showed that pre-service teachers’ behavioral engagement with web-based peer assessment differed depending on their revision operation and revision strategies. Overall, the pre-service teachers were engaged behaviorally with the correction they got from peers by doing revision operations and incorporating some learning strategies. However, we also found that the pre-service teacher did not engage behaviorally due to the lack of revision strategies. This study suggests that teachers or lecturers should give more practice regarding peer assessment in the classroom to enhance their behavioural engagement with peer assessment to improve their future writing.