Many scientists, policymakers, and other societal actors acknowledge the need to change food systems to improve human and planetary health, now and into the future. Increasing the supply and human consumption of grain legumes is an important strategy to orient diets towards health and sustainability. Enabling this shift requires an understanding of which actions are required, and who can do what. This thesis addresses questions, challenges, and actionable steps for future research and practice using the grain legume value chain. The grain legume value chain is embedded in the agricultural, knowledge and innovation system (AKIS), which conceptually organizes interconnected areas including innovation, agriculture, education and rural development. Sweden offers a rich contextual focus due to its capacity for grain legume cultivation and potential to increase consumption, typical of high-income countries in Northern Europe. This thesis is based on four articles in which I use qualitative and quantitative methods to investigate actors and actions at two food system scales – the grain legume value chain in Sweden, and a global multistakeholder initiative at the science-policy-society interface. In Paper I, I employ the leverage points framework to assess the potential of system-level actions in peer-reviewed and grey literature to increase grain legume consumption. I find that fewer actions address deeper leverage points with the potential to shift norms, values, and beliefs, and more actions focus on changes to production rather than consumption or a value chain approach. To link actions to actors, in Paper II I explore a novel methodology to determine what types of influence a set of actors in the grain legume value chain and AKIS have over these actions. Through semi-structured interviews and social network analysis, three types of influence are identified – self-perceived, attributed, and structural. Findings indicate that actors largely attribute influence to value chain or AKIS roles other than their own, and that few actors have all types of influence for any group of actions. Paper III further deepens the focus on actor agency, exploring how a set of actors in the grain legume value chain and AKIS perceive change happening and what types of power they have using social network analysis and semi-structured interviews. Findings suggest individual actors and actor groups may use types of power in different ways to facilitate or hinder changes to dietary patterns. Together, Papers II and III show that identifying actor influence and power beyond common approaches targeting size or market share can reveal opportunities and constraints to system change relevant for regional or sectoral efforts. Paper IV broadens the scope beyond grain legumes and Sweden, focusing on the outcomes of a multistakeholder initiative focused on healthy, sustainable, and just food systems in conjunction with the launch of the 2025 EAT-Lancet Commission. The analysis centers on the linkages between actor groups and actions from a cross-sectoral workshop, with particular attention to the role for national institutions, as well as principles of legitimacy and representational justice. Together, this thesis contributes methodological tools towards the larger goal of linking actors to responsibility for change as part of wider food system transformation processes.