To build a sustainable future, science and engineering education programmes should emphasise scientific investigation, collaboration across traditional science topics and disciplines, and engineering design, including design and evaluation of solutions. While some research studies articulate the shifts that are needed to realise classroom learning emphasizing investigation and design, fewer research studies help us to understand how we co-design these instructional programmes, including how experts from different essential disciplines collaborate towards an interdisciplinary instructional programme. We adopted a qualitative case study design to address the research question, "What is the process of team co-construction of instructional materials that emphasize learning through both science investigation and engineering design?" The paper outlines the first year of our team co-construction activities involving the design, implementation, and evaluation of instructional materials for secondary science. Qualitative data included semi-structured interviews with nine team members and documentation in form of researcher field notes and learning artefacts. Two cycles of coding resulted in five major themes that served as the basis for the five-phase model of team co-construction of instructional materials. This study provides information on the kinds of partnerships and collaboration needed to realise instructional programmes for students' study of the interdisciplinary STEM-based challenges of tomorrow.