The study examined an ESL writing class, which consisted of 36 students, at a community college of Hong Kong. The students took part in three online collaborative writing tasks by sending drafts to peers who gave them suggestions and comments for improvement and working together on the completion of the writing tasks via email. The 36 students worked in small groups of four to six. They wrote, responded and revised using the email system offered by the WebCT interface of their course book. The results were evaluated by means of questionnaire, interview with participating students, report of the peer observer, written work, e-responses and reflective summaries of students. The overall results suggest that students generally enjoyed the supportive atmosphere created by online collaborative tasks and regarded the use of online collaboration as a means of improving their writing by enhancing their motivation, awareness of the audience and the importance of revising, and by reducing their stress and cultivating their positive attitudes towards writing. The data show that the inclusion of the online component has potential in supporting learning and bringing about positive learning effects on writing as learners were found to enjoy the benefit of interacting with the other learners both in-class and out-of-class in the study.