Harry Redknapp fielded an attacking 3-5-2 line-up, with Hoilett operating in the hole behind Austin and Bobby Zamora in attack.
It was Hoilett that opened the scoring after 13 minutes with a cool finish inside the area before Austin doubled the advantage midway through the first half when he headed home Joey Barton's corner.
The next goal did not come until the 89th minute when Hoilett struck from distance, but there was still time for Austin to make it 4-0 with another headed finish from eight yards.
Before the game, Richard Dunne, who was born in Tallaght, was presented with a Shamrock Rovers lifetime season ticket as a gift, after he announced his international retirement earlier in the week.
QPR continue their preparations against Athlone Town on Tuesday night.