Chapman attacked on the fifth of eight laps around a 13.3km Surf Coast circuit in brutally hot conditions and rode away from three rivals in the final stages as the peloton threatened to close the gap.
"I'm a bit addicted to gambling in a bike race, it's true," Chapman said.
"Today it was just about having fun and really racing, you know, getting the race going."
The temperature soared past 39C and the heat was so intense Chapman helped out fellow leader Denisse Ahumada Riquelme (Agolico) by pouring water over her rival's head at one point in an admirable display of sportsmanship.
The pair held an advantage of more than two minutes over the peloton before Chapman left the struggling Chilean behind and put her foot down.
The FDJ Nouvelle Aquitaine Futuroscope rider was gradually caught by Lauren Stephens (Tibco), Tayler Wiles (Trek-Segafredo) and Emily Herfoss (Roxsolt-Attaquer), but blitzed the trio over the final kilometre.
"I often pretty much struggle in the first part of the race with all the intensity," Chapman said.
"As the race goes on, I find a bit of a rhythm and it really does come down to some self talk."
The inaugural Race Torquay has replaced Race Melbourne as the warm-up for the Cadel Evans Great Ocean Road.
Chapman gave her tick of approval to the fast Surf Coast course, which featured short, punchy climbs at the start of an otherwise relatively flat circuit.
Brodie Chapman took another gamble at the Tour Down Under, and although that one didn't pay off, we loved her attitude she expressed to us after the race: