Dean and his brother Dale snuck into a rodeo and saw a little fellow win $300 in calf roping. This gave Dean his sport. He felt that if a little fellow like that could win cash like that, this was for him as he was beginning to fill out to the 6'3", 200 lbs. frame he would carry throughout his career.
From practice in tying calves in mud an manure, roping bales at night, after his work in a dairy. With these God-given talents and fierce determination, he bought a horse and paid $10 for a practice calf.
After being denied a chance to compete in a rodeo in Winnemucca, Nevada he then joined the pro rodeo circuit and he was off to start his illustrious career. 1952-1953 was his first year on the tour and he learned plenty from other ropers and riders, and in 1955 he won his first world title in calf roping. In 1958 he won his second world title and also started to win in steer wrestling. Through the years Oliver won a total of 8 World Championships in calf roping, a record still standing. He also added 3 World titles as All-Around Cowboy and his career ended with 11 All-Around titles. As the age of 60, Dean still roped and trained horses and occasionally competed in senior rodeo events. He was also an accomplished golfer and he won many amateur tournaments.