The territory that currently corresponds to the Lisbon Metropolitan Area (LMA) has historically supplied fresh food to the urban population until half way through the 20th century. In 2018, the land use was still composed 38% of agricultural area, supplying 12% of the total food produced and consumed in Portugal. However, the operation of this food system is not subject to any regulations either in terms of spatial planning or land use management and, as such, its impact on sustainability transition in the region is not yet properly known. How to drive food transition in the LMA has thus arisen as a prominent question. In 2019, within a living lab context, the first steps were taken to this very challenging pathway, in which the definition of a food strategy was identified as the priority to sow the seeds of a food planning process. Over the last three years a food network started to operate on a collaborative basis to co-define a set of long-term objectives, a vision for 2030 and a collaborative biannual action plan. This article describes the process on how FoodLink—Network for the Food Transition in the LMA—leveraged the foundations to set up an evidence-based food strategy in the metropolitan area and how its thirty members became committed to cooperating in a science–policy–practice interface for its elaboration. According to principles of action–research and citizen science that implied a direct observation and involvement of the author along the entire process, the results intend to respond to the three objectives of the research by: (i) contributing to the literature on food networks; (ii) describing how the networking process occurred and its main achievements in what concerns a committed action plan; (iii) presenting the first baseline to pursue a food strategy towards the food planning of the city-region. It is understood that these results on how the food transition process is being driven in the LMA may either be inspiring for the construction of similar initiatives in other city regions, within and outside Europe, or may constitute the referential starting point for the future assessment of this ongoing transdisciplinary process.