Tatnell, a three-time Classic champion, started on the second row behind Lucas Oil’s Ian Madsen and Callum Zizek, before claiming the lead in the early laps of the race.
He was unchallenged for the remaining laps, winning the preliminary feature by more than two seconds.
Tatnell said his opening night success came down to a strong qualifying result and solid set up for the A-main.
“We qualified well and then won our first heat, which definitely helped,” said Tatnell.
“With the rubber down in the second round of heats, it was difficult to pass but we got enough points to keep ourselves up there.
“The boys gave me an awesome car for the feature. When you get a nice racecar, you can put anyone who can run the in top 20 in it and they’d be able to win.”
After his best ever start to the Classic weekend, Madsen leaves night one as the event points leader, but concedes he was unable to match Tatnell in the A-main.
“Brooke had the better car on the night,” Madsen said.
“I spent a bit too much time on the bottom line and got stuck in traffic, but it was still a great result for us.”
Sydney-sider Ian Loudoun rounded out the podium after making his way from eighth, but it was Warrnambool’s Jamie Veal who was the star of the show, charging his way from 17
thto fifth position in a commanding drive from the B-Main.
Defending champion, American Tim Kaeding has had to withdraw from the rest of the weekend after being taken to hospital as a precaution following a heat race accident.
Robbie Farr started the night on the front foot, setting the quicktime in qualifying and winning the opening heat.
Tatnell, Madsen, Terry McCarl, Daniel Pestka, Matt Dumesny, Danny Holtgraver, Darren Molleniyux, Brendan Balcombe and Trever Green also recorded heat wins.
Night two of the Lucas Oil Grand Annual Sprintcar Classic takes place tomorrow, with qualifying from 6pm and racing from 7pm. Live streaming is available from www.thecushion.com.