Oatmeal has a long history in Scottish society because oats are better suited to the short, wet growing season of Scotland than is wheat. Hence oats became the staple grain of that country.

Samuel Johnson referred to this in his 1755 dictionary definition for oats:

A grain, which in England is generally given to horses, but in Scotland supports the people.

To which his biographer, James Boswell, added:

which is why England is known for its horses and Scotland for its men.