Educational attainment is a key determinant of diet quality. The overarching pathways (i.e. theories and mechanisms) through which educational attainment shapes diet quality remain largely unexplored in the nutrition literature, and the most salient pathways likely differ across time, populations and socio-economic and political contexts. This commentary proposes a research agenda and outlines methodological considerations that are intended to better illuminate the educational attainment–diet quality relationship. From an extensive review of the literature, which led to two publications pertinent to the topic, we identified three major research gaps that should be addressed to better understand how educational attainment stratifies diet quality to guide interventions and inform equity-enhancing policies: (1) interrogating the construct of educational attainment; (2) comparative population–level and subgroup studies; and (3) root cause analyses and structural reforms. We also discuss methodological considerations needed to inform future studies of associations between educational attainment and diet quality.