The 32-year-old struck home a precision free kick in the 25th minute to open the scoring, emphasing his role as the team's talisman with a superb effort in Cardiff.
A deflected shot from Marcel Sabitzer in the 64th minute offered Austria hope of a comeback as a wasteful Wales endured a nervy finish but the home side held on for a deserved win to stay on course for only their second World Cup appearance.
Bale lifted the atmosphere and propelled his teammates to victory with a superb left-footed free kick from outside the penalty area that dipped dramatically into the top corner of Heinz Lindner's goal.
Wales, World Cup quarterfinalists in 1958, survived a scare when Christoph Baumgartner slammed the ball against the bar in the fifth minute but once Bale had opened the scoring they found their rhythm and were able to create numerous chances.
Their pressing and counter attacking game offered opportunities, especially five minutes from half time when Aaron Ramsey sprinted upfield only to see his shot expertly turned around the corner by a diving Lindner.
The Austrian also made two important second half stops from breakaways led by Daniel James but could do nothing about Bale's close-range shot that doubled the score six minutes into the second half.
A short corner routine saw the ball played into the box where Ben Davies looked to bring it under control but Bale stole it off his teammate, turning to slam the ball home.
Real Madrid forward Bale should have had a hat-trick on the counter attack just past the hour mark but his left footed effort sailed wide over the target.
Austria reduced the Wales lead when Sabitzer was given time to shoot from outside the area with the effort deflecting off Davies and wrong-footing goalkeeper Wayne Hennessey.
It threatened to make Wales pay for squandering their chances but they held out and might have added a third right at the end when Lindner made another fine stop to deny Ramsey.