This study investigated how cluster initiatives’ members contribute to cluster initiatives concerning tasks as well as what dependency patterns exist between maturation level and enrolment of members in these organisations. The content of the work is considered as crucial for organisational functioning and development. The findings are based on survey responses from 136 (53% response rate) cluster initiatives from eight European countries. The results show that, first, all members contribute to initiatives’ development by performing strategic, operational tasks, and provision of resources. Each member tends to focus more on one task than the others that are delegated. Second, two factors influence enrolment of new members in cluster initiatives: age and presence of other influential members. The more mature cluster initiatives become the more networks and established organisational attributes it will have. This reflects longevity of the initiative and good-quality, intermediary assistance, which are attractive for potential members.