McLeod - the 2018 PGA Tour of Australasia Order of Merit winner - regained his card at the Qualifying School in the autumn, while fellow home favourite Smyth achieved his best ever European Tour finish last time out at the Australian PGA Championship.
They both carded bogey free rounds of 65 on the Creek Course to get to seven under.
European Tour winner Ryan Fox was then in a group of seven players at five under.
This week's event sees the field playing the Creek and Beach Courses on days one and two before all play switches to the Beach after the cut.
It also features concurrent tournaments for men and women playing for equal prize money and in the women's event, South Korea's Haeji Kang and Swede Madelene Sagstrom shared the early lead at eight under.
McLeod made a fast start with birdies on the first and second and never looked back, adding further gains on the seventh, ninth, 11th, 13th and last.
Smyth also birdied his first two holes and picked up shots on the sixth, seventh, ninth, tenth and 14th.
Griffin and Warren also had clean cards as they made seven birdies to share top spot.
Frenchman Sciot-Siegrist was out in the very first group of the day and made seven birdies and a single bogey on the Beach, while Canadian Cockerill was bogey free on the same layout.
Lee finished third at the Australian PGA Championship and he recovered from back to back bogeys on the back nine to come home in 31 after starting on he tenth on the Creek Course.
Evans had led the way at eight under but double bogeyed the last.
New Zealander Fox had his wife on the bag after his regular caddie fell ill and he carded an eagle, five birdies and two bogeys to sit alongside fellow Kiwi Gareth Paddison, Dutchman Will Besseling, Northern Ireland's Jonathan Caldwell, American Derek Ackerman and Australians Simon Hawkes and Shae Wools Cobb.
Defending champion David Law was then in the group at four under.