Writing across the curriculum (WAC) is a way of integrating the teaching of writing into specific academic disciplines. A problem faced in the WAC literature is how to develop a process that integrates the skills of multi-disciplinary teams. In this project, action research was used to develop a team comprising faculty from the applied sciences and a writing teacher which had been commissioned to integrate the teaching of writing into an undergraduate horticulture course. Five features of action research were of particular importance: the foci of change and collaboration, the rational, systematic process it provided, the locating of the research in a real as opposed to controlled context, and the dual foci of action and research. Action research provided a successful process and structure for the project: outcomes included changed attitudes to writing amongst students and a deeper understanding of how students value written assessment. Unexpected outcomes included spontaneous participation of students in the action research process, the provision of useful methods of reflection for teaching staff, and the development of professional trust amongst faculty from different disciplines.