Oreo, a 481 kilogram Speckle Park/Angus steer, beat 70 other steers at the Show to the top prize with a score of 92 points out of 100, after already winning the heavy domestic carcase class.

Queanbeyan High Agriculture teacher Ian Crabb said it was a narrow win of just half a point over heavy weight rivals, St John's College from Dubbo.

"I was very, very proud of the students and the way they presented their animals last week," Mr Crabb said.

"It is no easy task to program the correct amount of feed, seven days a week for five months to have the ideal amount of fat on the animal on a particular day in its life.

"There have been lots of congratulations rolling in. I've been passing them on to the students, because they're the ones that are there recess and lunch times putting the effort in," he said.

Oreo's journey to grand champion began when School farm assistant and cattle producer John Slater spotted a calf with potential at the Braidwood saleyards in July last year. He bought the pen, but did not bring the steer into school until he was sure that it had the right temperament to work with the students.

Agriculture students from years 7-12, along with the specialist show team of senior students then fed, groomed and trained Oreo and two other steers over the last five months leading up to the Show.

The steers were judged live last week, with judge assessing how much muscle and fat they thought each animal was carrying. Oreo placed third in the heavy domestic class, while James, a Limousin-Angus cross was third in the heavy export class. The steers were then auctioned and trucked to Cootamundra for slaughter.

With the skins off, the quantity and quality of meat and fat could be measured. Oreo scored 92 points to win his class, while James scored 87.5 points to take second place in the export class. Oreo then competed against the winners of the light and medium domestic classes plus the export class winner. Oreo had the highest score and was awarded Grand Champion carcase of the Show.