This paper describes a design-based research study in which an online platform for teachers was designed and implemented over 3 years. The study uses a networked learning approach to support teachers in the transition from university into service. It addresses the question of how online communities of teachers can support the development of situational knowledge. The paper describes the potential and the challenges of designing and implementing learning networks for teachers. A major challenge identified is the need for design that supports trust and stability within large networks. Significant potential is identified through the reuse of knowledge and greater collegiality within the profession. The platform, TeachConnect, was developed as a collaboration between academics at eight Australian universities, to create a platform to support teachers across the boundary from preservice into the profession. The study presents results from design and implementation, and includes site usage statistics and coding of types of support present within the platform. The paper contributes design principles for online communities of teachers and raises theoretical questions about future online communities.