From the 1755 edition of Samuel Johnson's Dictionary :

OATS n. s. [aten, Saxon.] A grain, which in England is generally given to horses, but in Scotland supports the people.

It is of the grass leaved tribe; the flowers have no petals, and are disposed in a loose panicle : the grain is eatable. The meal makes tolerable good bread.
--- Miller
The oats have eaten the horses.
--- Shakespeare
It is bare mechanism, no otherwise produced than the turning of a wild oatbeard, by the insinuation of the particles of moisture.
--- Locke.
For your lean cattle, fodder them with barley straw first, and the oat straw last.
Mortimer's Husbandry.
His horse's allowance of oats and beans, was greater than the journey required.
--- Swift