The advantages of collaborative writing on students' writing correctness have received much attention from researchers, but the benefits of this method on students' writing fluency have not been shown. Not only that, but no research up until now has looked at how students might work together to write argumentative essays. This essay aims to address such knowledge gaps. A total of 62 college sophomores with an English major participated in the research. One area where the two groups were treated differently was during the writing phase. While the 25 students in the control group worked together on an outline and developed ideas for an essay, the thirty-five students in the experimental group wrote their papers as a group. The pre-tests, post-tests of both individually and jointly produced papers, and the semi-structured interviews administered to the students provided the data for this study. The research finds that students' writing fluency improved significantly in group and individual writing tasks after engaging in collaborative writing. In addition, the research developed a helpful framework for collaborative writing tasks that may be used in writing schools.