Despite concerted efforts, achieving the goal of universal food security remains challenging. Food security interventions occur at different levels of systemic depth. Some interventions target visible supply-side gaps, while others focus on deeper systemic problems in the food system. Here, we used a leverage points perspective to ask how multiple types of more superficial (shallow) and more fundamental (deep) interventions in the food system interact. Focusing on a case study in southwestern Ethiopia, we examined (1) recent changes in formal and informal institutions related to food security; (2) the effects of formal and informal institutions on the food system at different levels of systemic depth (i.e., on parameters, feedbacks, design, and intent); and (3) issues of institutional interplay between formal and informal institutions. We surveyed 150 rural households and analyzed key policy documents. Both formal and informal institutions were perceived to improve food security. However, at the intent level, formal institutions primarily aimed to enhance food supply, while informal institutions additionally sought to build trust among farmers. At the design level, formal interventions targeted information flow through a newly created agricultural extension system, while informal institutions facilitated labor sharing and communication. In terms of institutional interplay, new formal institutions had partly undermined pre-existing informal institutions. We conclude that both visible supply-side gaps and deeper drivers of food insecurity should be targeted through food security interventions. Interventions need to be cognizant of potentially unexpected ways of institutional interplay, especially between formal and informal institutions.