The rubric is an effective instrument for making assessment criteria explicit, and for helping ensure fairness in grading. The use of rubrics for peer evaluation in cooperative class environments can offer the same benefits. This study analyzed student-developed criteria for a peer evaluation rubric in order to determine the elements that university students valued most in the cooperative activity of Problem-Based Learning. Nineteen university students participated in the study, and the major tool for categorizing the characteristics of peer evaluation was a modified version of both the Teamwork Skill Inventory and the Category-based peer evaluation framework. Findings indicated that the category of Attends to Teamwork, Motivation, Responsibility, and Time Management was the most frequently applied category for the peer evaluation rubric related to team activity. The study also provided additional details about the criteria utilized in all seven categories developed for this peer evaluation rubric.