Due to growing concerns regarding the effectiveness of full-scale online education, this study investigated motivational regulation strategies employed by tertiary-level English as a foreign language (EFL) learners taking a writing course via Zoom. Using a mixed method, this study examined a dataset comprising questionnaire responses of 154 Korean students with two proficiency levels and subsequent semi-structured interviews. Findings showed that the learners with a high English proficiency level utilized the instructor's feedback significantly more than those having a low proficiency level. The high proficiency group also appreciated the Zoom context and the universitywide policy of English-medium instruction (EMI) significantly better than the other group. Finally, correlation analysis revealed significant relationship between the students' uses of motivational regulation strategies and their responses to the context-dependent factors. For example, the strategic choice of instructor feedback was positively related to their perception of EMI. These findings are discussed for effective online EFL writing instruction in the post-pandemic era.