In recent decades, web-based collaborative writing has become popular as a technical technique for improving collaboration. The study explored the effect of Google-mediated collaborative writing (henceforth GMCW) and face-to-face collaborative writing (henceforth FTFCW) on developing English as a Second Language (henceforth ESL) students' global and local writing features (organization, development, cohesion, structure, vocabulary, and mechanics). Despite the emphasis English language instructors in Saudi universities place on writing skills, students still face challenges in achieving proficiency in writing. The study included 46 male students at level 3 from the Qassim University English Language Department. An experimental study was used, along with a post-questionnaire, as additional material to collect students' perceptions. In addition to using the independent t-test to compare the mean in the post-test of the two groups, a paired t-test was used to compare the mean in the pre-test and post-test of the same group. The researcher used a two-by-two mixed ANOVA to examine how students' global and local writing features (such as organization, development, and cohesion) changed when they collaborated face-to-face or via Google Docs. The results showed that the Google-mediated collaborative writing post-test mean was greater than face-to-face collaborative writing in all writing features, and the difference was statistically significant. The questionnaire revealed that Google-mediated collaborative writing raised confidence, encouraged teamwork, instructed students on how to engage in peer feedback, and increased their willingness to use Google Docs for further assignments. Google-mediated collaborative writing benefited students more in terms of their writing quality (organization, development, and cohesion) than their writing accuracy (mechanics and structure). Google-mediated collaborative writing did not pay attention to form (spelling, punctuation, or structure). In contrast, students' perceptions of the global and local writing aspects of face-to-face collaborative writing negatively impacted organization, development, and cohesion. The face-to-face collaborative writing students focused more on the essay form (mechanics and structure) than on the content (organization, development, and cohesion).