Researchers and policymakers are increasingly employing the concept of entrepreneurial ecosystems to understand the concentration of high growth ventures in certain regions. Ecosystems represent the economic, social, and policy environment surrounding the entrepreneurship process. Public and privately run entrepreneurship support organisations (ESOs) form a critical part of entrepreneurial ecosystems by providing training and resources to entrepreneurs and new ventures. However, the role of ESOs within ecosystems is poorly understood with little conceptual or empirical discussions about how they contribute to the development of successful entrepreneurial ecosystems. To address this gap this paper employs the concept of institutional thickness to identify the optimum structure of support programs within a region. The role of institutional thickness is explored through an investigation of entrepreneurship support programs aimed at technology entrepreneurs in Edinburgh, UK. 43 ESOs are identified and their actives and types of support they provide analysed. The paper argues that there is the need for a new approach to the role of ESOs within ecosystems that looks beyond a single program but instead embraces a more holistic perspective that sees how they work in conjunction to provide support for firms throughout the venture creation and growth process.