This research focused on the common errors that EFL learners included in their writing. The frequent errors that the study focused on were at the micro level, specifically the structures that related to gerund and infinitive forms. The participants were selected from the English language department at one of the Saudi universities. They were undergraduates and passed the "English Grammar 1" course in the program and were ready for the "English Grammar 2" course. In this study, the participants passed through two phases. In the first phase, they wrote one paragraph individually in the midterm examination. In the following phase, they chose their group and wrote a paragraph during class time. In both phases, students received clear instruction including the topic, the grammatical rules, and the minimum number of sentences. The only difference was that students were allowed to discuss for ten minutes before writing their paragraphs in the second phase. To analyze the data, common errors were identified and classified from writing as groups and individual writing based on gerunds and infinitives. Then, the comparison between common errors was employed to understand learners' written production when working individually and in groups. The results indicated that learners easily used infinitives better than gerunds. Learners also overused specific words to ensure that they used gerund and infinitive in the correct form. Finally, the same common errors were found and identified in their individual writing and as groups.