This mixed-methods study explored the students' learning from the task-based collaborative writing process (Ellis, 2003; Willis, 1996) and the effects of its process on their writing improvement in a compulsory academic writing course. Due to the Covid-19 pandemic, this course was conducted completely online. This 15-week course followed the parallel sessions of (1) the instructor lectures for the writing practices and student practices of collaborative writing in class, (2) students collaboratively write their first draft outside classroom, (3) the instructor's oral and written feedback for the first draft of students' work, (4) online group conference among group members to collaboratively reflect their own learning from instructor feedback, and (5) collaborative revision of the first draft before submitting a final draft. These sessions recurred four times during the course when the students worked on each assigned task that made up a group project. These four writing tasks included a research proposal, a literature review, a report of interviews or surveys, and discussion of the findings. At the end of the semester, all groups orally presented their projects. Data were collected from two drafts of all four essays, group conferences with the instructor, and dialogues during group reflection conferences. Overall, the participating students were found to have positive perception of the task-based collaborative writing because it allowed them to have a deeper understanding of the research process and improve the content and organization of their writing. Implications suggest aspects of the process that contribute to the students' positive perceptions and writing improvements.