The wild ancestor of Avena sativa and the closely related minor crop, A. byzantina, is the hexaploid wild oat, A. sterilis. Genetic evidence shows the ancestral forms of A. sterilis grew in the Fertile Crescent of the Near East. Oats are usually considered a secondary crop, i.e., derived from a weed of the primary cereal domesticates, then spreading westward into cooler, wetter areas favorable for oats, eventually leading to their domestication in regions of the Middle East and Europe.

Oats are best grown in temperate regions. They have a lower summer heat requirement and greater tolerance of rain than other cereals, such as wheat, rye or barley, so they are particularly important in areas with cool, wet summers, such as Northwest Europe and even Iceland. Oats are an annual plant, and can be planted either in autumn (for late summer harvest) or in the spring (for early autumn harvest). Source: Wikipedia