Mr Cox takes on the role from Roger Desailly who left the organisation following the May event.
Beef Australia expos are held in Rockhampton every three years.
The next beef expo will be in 2015.
This year's Beef Australia 2012 was regarded as the most successful in the event's 23 year history, attracting some 85,000 visitors.
Mr Cox has had extensive experience as an event and sponsorship manager. He previously worked with the Melbourne Racing Club and was the sales and marketing manager at Moonie Valley.
Mr Cox will start in his new role with Beef Australia on October 22.
Mr Denis said he would initially focus on organising sponsorship with his staff of three. The team will grow to 20 and 30 staff nearer the event, he said.
Mr Cox said his last day with the Rockhampton Jockey Club would be St Peter’s Caulfield Cup Day on Saturday October 20.
"I wanted to stay on until this time to ensure that our biggest day of the year (5000 patrons) is a huge success," Mr Cox said.
"I will also be available anytime afterward to the new CEO and staff to ensure a smooth changeover."
Mr Cox said he had not been lost to the sport of racing.
"I’m planning on becoming a Member and attend race meetings socially," he said.
"Thanks again for all your support and I look forward seeing you at the track soon."
The Rockhampton Jockey Club is now seeking a new chief executive officer. The RJC holds 47 race meetings each year at its Callaghan Park Racecourse.