This paper presents an overview of a large scale research project involving teachers and students across eight European countries and involving eleven partner organizations. The project was focused on helping equip students with key transversal skills and competencies. We used integrated STEM as a site to ground the development of these interdisciplinary ways of thinking, being and doing and digital tools as ways to help teachers deepen and enhance their formative assessment practice. We present here an out line of research conducted to develop a framework for conceptualising integrated STEM skills and their assessment via digital tools. This framework identified a number of core competencies and ways to both design and assess for these skills using digital t ools. We also give an account of subsequent professional development with teachers and the piloting of developed teaching methods in schools. The next phase was the conduct of evaluations of our work according to a research methodology which aimed to ident ify best practices for scalable teaching. Some emergent findings and lessons learned along the way from two countries, Ireland and Sweden, are presented as examples here as we complete the analysis stage of the project. This paper aims to contribute to the conversations around interdisciplinary and integrated STEM skills, how they can be digitally assessed and to give an account of the workings of the associated large scale research project. Keywords: STEM, Integrated STEM, inservice teacher education, transversal skills