Recently, wikis have been claimed to facilitate collaborative-writing projects and bring positive impact on student learning. While most previous exploratory studies conducted in L2 classrooms focused on students' perceptions and their collaborative process, students' produced texts have seldom been carefully examined from linguistic perspectives. To aim towards a more comprehensive understanding of wiki-based collaborative writing, this study compares collaboratively and individually produced texts, explores the nature of the two different writing processes, and investigates students' perspectives. An intact class of eighteen EFL college students participated. They completed two writing tasks collaboratively and individually on wikis. Both qualitative and quantitative measures were adopted to analyze the data in order to probe students' writing products, composing processes, and perceptions. Results of this study revealed that wiki-based collaborative writing tasks have offered students good opportunities to learn from each other and students believe such collaborative activities improved their writing.