In the past decades, collaborative game-based learning has been used to facilitate students' learning in authentic learning contexts. Although several previous studies have reported the potential of this approach for students' learning performance and motivation, unequal participation could negatively influence the learning effectiveness of collaborative learning. To this end, this study developed a mandatory contribution-based collaborative gaming approach (MCCG) to enhance the competencies for conducting practical solutions related to environmental issues during a cross-field learning activity between a school and a museum. MCCG and a conventional collaborative gaming approach (CCG) were implemented to investigate the effects of individual contributions on collaborative learning. Both individual learning achievements and collaborative learning outcomes were assessed. The results showed that game-based collaboration supports can support competency-based education to enhance students' competencies, such as problem-solving and critical thinking competencies. Those students who learned with the mandatory contribution approach had better collaborative learning outcomes.