The purpose of this empirical study was to explore the interactional commenting patterns that EFL learners produced in web-based peer feedback and correlate them with the learners' writing achievement. The study employed a quasi-experimental design built on the Theory of Cognitive Apprenticeship (Collins, 1991), which gives emphasis on coaching (local revision) and scaffolding (global revision) processes. The context of the study was in a public university in Oman and 50 participants were involved in a selected range of online peer-feedback processes, synchronously and asynchronously. A paired samples t-test showed that students were able to improve their grammar range and accuracy in writing essays more than other scaling categories (e.g. content and organization). The results of the qualitative analysis indicated that students produced far more comments synchronously than asynchronously, and most of the students' exchanges were on forms. The findings of this study could be a practical reference for those who plan to cultivate the use of technology in peer feedback practice.