Geese are grazers at heart — you will often see them cropping grass like little lawnmowers. Their diet is mostly plants, which sets them apart from many other water birds.
What geese eat in the wild
Geese are largely herbivores. Their natural diet is built around grass, aquatic plants, roots, grains, seeds and berries, and they graze on land as readily as they feed in water. They do eat the occasional insect or small water creature, but plants make up the bulk of what they eat.
Don't feed geese bread
As with ducks, bread is a poor food for geese. It fills them up without proper nutrition, can contribute to deformities in goslings, and fouls the water when it rots. Geese fed a lot of bread can become unhealthy and overly bold around people, so it is best avoided entirely.
Better foods to feed geese
If you feed geese, stick to foods close to their natural, plant-based diet: cracked corn, oats, wheat, birdseed, and chopped lettuce, cabbage or other leafy greens. Offer small amounts on the grass or water surface, and only what they will finish, so nothing is left to spoil.