The outbreak of COVID-19 has made a substantial positive impact in educational settings, urging teachers to use innovative online ways of teaching and making numerous online platforms, including Microsoft Teams, Google Meet, Google Classroom, video communication applications, and many other tools accessible for students. However, the online learning setting has spawned a variety of challenges for both learners and teachers, ranging from technical problems to poor training. As a matter of fact, learners, educators, and practitioners have different attitudes toward the effectiveness of online learning. Considering this, this study investigates the impact of implementing online learning on students' grammar performance in Morocco. It does so by assessing the control and experimental groups' performance during five-week experimentation. The study population was 11th-grade secondary school students in Tazizaoute High School, El Kbab, Khenifra, Benni-Mellal-Khenifra Region. The participants were randomly and equally assigned to the control group (N=30), taught through face-to-face learning, and the experimental group (N=30), taught using online learning via Microsoft Teams. To collect quantitative data, grammar pre- and post-tests were employed to measure the grammar performance in both groups before and after the treatment. Both descriptive and inferential statistics (Independent T-Test) using SPSS-26 were used to analyse the data. The findings revealed a statistically significant difference between the two groups favouring the control group.