The diet of Orange-breasted Bunting has not been studied in detail in the wild, but the diet in captivity has been compiled for the cage-bird trade.
Sorderberg (1956) recommends a diet based on canary and white millet, with a lower percentage of other seeds, such as hemp and thistle, although they will eat no yellow millet. Insects are recommended whenever possible, especially live ant cocoons, although mealworms in excess will make the birds overly fat (Sorderberg 1956). They are also very selective about which fruits they eat, but favor for hard, sweet apples (Sorderberg 1956), although whether this is actually representative of their diet in the wild is debatable.
It is likely that the Orange-breasted Bunting has a diet similar to other members of its genus. Hutto (1994) indicates that it is a seed-eating bird, while Sorderberg (1956) does mention that it will eat wild grasses. Stomach contents from a closely related species, Painted Bunting (Passerina ciris), suggest that this bird’s diet is over 70% vegetable material, especially seeds, while the rest comes from animals, mostly insects (Lowther et al. 1999).