What percentage of corn do you use with oats to feed beef cattle?

None. If you get enough energy content with feeding oats (especially processed oats), corn is not necessary. However, it depends on the class and breed of beef cattle you are referring to, as well as environmental factors, additional feedstuffs given and accessibility. As such, a person could include anywhere from one percent to as much as 80 percent corn used with oats to feed beef cattle.