They capitalised on turnovers and many missed tackles, skillfully sending the ball out wide.
Centre Jaco Taute and prop Caylib Oosthuizen earned the well-beaten Lions a scrap of respectability with last quarter tries.
Sparked by dangerous five-eighth Lealiifano and lively back rowers Michael Hooper and Foto Auelua, the Brumbies were far too clinical for the mistake-ridden Lions.
The Brumbies led 17-6 at the break, following tries to prop Ruaidhri Murphy, winger Henry Speight and centre Andrew Smith, but missed ten points worth of kicks, with Lealiifano also butchering a try by dropping the ball over the line in a tackle.
Tries to winger Joseph Tomane and Ben Alexander early in the second half put the Brumbies well clear and Speight crossed for his second just before the hour mark.
The Brumbies didn't add to their score in the final quarter despite Lions reserve back Butch James earning both yellow and white cards for an illegal shoulder charge.
-AAP