The competition tis held annually at Centenary Oval and it consists of a round robin lightning football tournament with representative teams of leagues from the Eyre Peninsula and beyond.
Named after William Tennant Mortlock, the Mortlock Shield began in 1936 when the football associations of Central Eyre, Cleve, Eastern Eyre, Great Flinders and Port Lincoln decided to hold a football tournament to celebrate the centenary of South Australia.
Since 1994 The best players from the carnival are selected represent the Eyre Peninsula team in the SA Country Football Championship.
The current format of the Mortlock Shield consists of a single round robin structure composed of 5 representative sides of football leagues from around the Eyre Peninsula.
The team on top of the ladder after four games played is declared champion and awarded the perpetual Mortlock Shield to commemorate their win.