Across all nations, undergraduate psychology programmes aim to promote the acquisition of foundational psychology competences. Yet, until recently, a universally recognised model outlining essential competences did not exist. The International Collaboration on Undergraduate Psychology Outcomes (ICUPO) addressed this gap by developing the International Competences for Undergraduate Psychology (ICUP) Model. The aim of this article is to provide guidance about how other groups might successfully approach similar efforts to delineate discipline-specific key competences. We describe the processes that led to the development of the ICUP Model, framed by group development theory (Preparing, Forming, Storming, Norming, and Performing Stages), with additional consideration of individual ICUPO Committee member psychological needs for competence, relatedness, and autonomy. Each group development Stage section (a) describes project activities relevant to the characteristics of that Stage, and (b) lists key strategies employed and lessons learned, as well as commentary on psychological needs. To further enhance the value of this endeavour, the Discussion includes (a) commentary on the strengths and limitations of these theories for understanding and enhancing the effectiveness of such project processes, and (b) actionable insights for educational leaders undertaking similar projects.