The coronavirus (COVID-19) pandemic disrupted the food supply, distribution and services and led to major changes in the federal government’s safety-net programs. This paper synthesizes evidence for the literacy needs of Supplemental Nutrition Assistance Program (SNAP) eligible adults who receive benefits from the United States Department of Agriculture (USDA) to purchase groceries in an online food retail ecosystem. We examined 40 literacy frameworks to develop a multi-dimensional, five-step, digital food and nutrition literacy model that included functional, interactive, communicative, critical and translational literacy. We used the model to review and evaluate 18 U.S. food and nutrition literacy studies. While adults with higher food or nutrition literacy scores had better cognitive, behavioral, food security or health status outcomes, there were no consistent findings across the studies. No frameworks examined digital literacy, three studies reported using a conceptual framework, and six studies examined SNAP or SNAP-Education (SNAP-Ed) outcomes. Future research should test this multi-dimensional food and nutrition literacy model, validate metrics to measure progress to achieve the outcomes, and develop dissemination tools tailored for SNAP participants. Diverse strategies could be implemented by U.S. government agencies, retailers, foundations and non-governmental organizations to strengthen digital literacy and the infrastructure for a healthy online food retail ecosystem.