Canada geese most actively feed during the early morning and late afternoon. They are grazers and eat a variety of plants such as marsh grass, berries, sprouting wheat, bulrush, glasswort, salt grass, brome, clover, salt brush, cattails, not to mention turf grass.

Geese are often seen with their heads underwater and tails in the air; at these times they are typically feeding on tubers, roots, leaves, seeds, widgeon grass, algae and various pond weeds. When feeding in this manner, many geese swallow lead shot left behind by hunters' guns. Geese poisoned by lead die a slow and painful death.

The diet of geese that live in coastal areas can also include mollusks and small crustaceans. In the fall and winter, geese sometimes eat leftover grain that remains in farmers' fields; they are especially fond of corn.