The energy transition requires rapid deployment of complex infrastructure, yet many projects - such as carbon capture hubs and HVDC interconnectors - face persistent cost overruns, delays, and learning bottlenecks. While organizations recognize the need to learn from past efforts, they often lack the internal structures or cross-project mechanisms to do so effectively. This thesis investigates how specialised intermediaries can improve inter-organizational learning and accelerate energy transition delivery. It addresses the question: How can the energy sector make use of intermediaries to improve inter-organizational learning and accelerate the energy transition? The study adopts an exploratory, qualitative multiple-case design, examining three energy projects where Turner \& Townsend acted as intermediary. Data were collected through fifteen semi-structured interviews with both client and consultant representatives and analysed thematically to identify learning mechanisms, barriers, and outcomes. Findings show that intermediaries were engaged to close capability gaps, deliver structured benchmarking, and adapt proven delivery models to novel technical contexts. Through a mix of codified frameworks (e.g., the Cube methodology), anonymised data platforms, and embedded expertise, the intermediary helped project teams standardise fragmented inputs, challenge assumptions, and institutionalise improved routines. This accelerated learning from one project to the next and strengthened long-term client capabilities. The thesis introduces a “Build–Partner–Burst” model to explain how intermediary involvement can adapt over time to meet evolving project needs. The study contributes to intermediary and organizational learning theory by showing how intermediaries act as configurable capability platforms that compress learning cycles, substitute for slow trust formation, and make sector-wide knowledge sharing more viable. Practical recommendations include earlier intermediary engagement, investment in digital data infrastructure, and more deliberate context-tailoring of delivery tools. While limited to three cases within one firm, the findings suggest that intermediaries can play a catalytic role in scaling learning across projects and organizations in the global energy transition.