This article describes a study of online collaborative design in the context of teacher professional development. Twenty-five teachers from different Spanish universities participated in the online course. The aim was to understand how to support teachers in interuniversity teams to collaborate fully online throughout the learning design process of a scenario based on their discipline integrating information and communications technology (ICT), an issue scarcely tackled in the literature. The described interpretive study, using mixed methods, explores the support of online co-design provided by a novel ICT community platform named ILDE (Integrated Learning Design Environment). Lessons drawn from the results can contribute to the improvement of online collaborative design processes in the context of teacher professional development.