Cereal companies had wheat, corn, and rice, but none had a cereal with an oat base until 1941. CheeriOats were introduced as a “ready-to-eat” oat cereal. The name emphasized the main ingredient to differentiate itself from the other types of cereals.
Unfortunately for CheeriOats, Quaker Oats took offense to the name,
claiming the “Oats” part infringed on their trademark. To avoid a
potential lawsuit, the name was changed to Cheerios in 1945. It had
a mascot named Cheeri O'Leary, but that was quickly dropped. In
1949, the Lone Ranger radio show needed a sponsor. General Mills
obliged and the association with the Lone Ranger lasted for 20 years
and helped propel Cheerios into the most popular breakfast cereal.
The shape inspired the updated name. The “O” shape was made by a
specially designed “puffing gun”. Cheerio dough is heated and
rapidly and shot out of this gun, which makes the dough puff into
the “O” shape.
By 1951 Cheerios was the top-selling cold cereal sold by General
Mills. Cheerios continues to dominate the cereal market with about
one eighth of all cereal sales in the United States. It is sold in
over 130 countries. Other varieties of Cheerios introduced over the
years include honey nut, apple cinnamon, multi-grain, berry burst,
fruity, banana nut, chocolate, and frosted.