Online learning democratizes and provides flexibility in accessing education, but it also places greater demands on students' self-regulated learning strategies. Previous studies have explored the important impact of effort regulation on academic performance. However, there remains more to explore on the dynamics of effort regulation among undergraduates and their group differences. This study investigates how the effort regulation of the learning process varies between achievement categories in an online learning environment using a sample of 240 undergraduates. Findings suggest that students in the high-achieving group had significantly higher effort regulation throughout the semester than their low-achieving counterparts on three dimensions: conversation, navigation, and click-through events. However, there were no significant differences in task time. Further test results also show that the high-performing students had significantly higher levels of engagement in all behaviours compared low-performing students during anaphase. Surprisingly, all students significantly lowered their effort levels near the final exam period. Results herein ultimately provide insight into the design of online learning environments.