In the 21st century, preparing university students for real work and lifelong learning requires instructors to serve as facilitators of learning rather than as providers of information. Instruction needs to be learner-centered, active, enjoyable, and engaging. As one form of active learning strategy, cooperative learning (e.g. group assignment) helps students to collaborate in tasks actively, and this in turn improves their learning and performance. However, in my undergraduate course, when I encourage students to do assignments in groups, many of them do not take it seriously and, as a result, the final product is in terms of quality and participation. The objective of this action research was to improve the educative value of group assignment as one form of cooperative learning by way of designing the task thoughtfully, following up and motivating students, providing constructive and timely feedback, and ensuring greater student engagement in the task. Third year psychology students were enrolled for the project, and two phase actions were implemented: preliminary and actual action implementation. The outcomes of the preliminary and actual action implementation were then compared. The findings revealed that, as a result of the intervention, students changed their attitudes towards group assignment and were more engaged in the second assignment than the first (t = 6.51, p = 0.05). Students' performance in the second test and group project also increased (t = 2.80, p = 0.05 and t = 7.67, p = 0.05 respectively). Based on the findings, implications for future research and action are suggested.