REIGNING premier Brisbane will defend its title against Geelong in next week's Grand Final after defeating Collingwood 15.10 (100) to 11.5 (71) at a packed MCG on Saturday night.

There was plenty of fire in the first quarter as the two most recent premiers lifted to full finals-level pressure, with Brisbane coming out in front on the scoreboard.

Trailing by more than three goals at the first change was bad enough for Collingwood, but the pain was multiplied by the early substitution of inspirational veteran Scott Pendlebury, out after five minutes with a calf issue.

The second quarter was a complete reversal of form and fortune, the Magpies doing everything right with the ball while the Lions were struck by injuries.

Jarrod Berry went down with a nasty shoulder injury that required inspection by the AFL's own doctor, the midfielder removed from the game and Bruce Reville subbed in.

Meanwhile, Collingwood went about reining in the deficit, taking the lead and then extending it to 13 points at half-time.

The script remained predictably unpredictable in the third as Brisbane kicked the next four goals, the run only broken by a Jamie Elliott goal after what would have been a mark of the year favourite if taken during the home and away season.

All that, plus another goal each way, and the term hadn't yet reached the halfway mark.

When the siren sounded for the final change the Lions sat three goals in front, but in the fourth quarter the Pies were kicking to the end where 17 of the 20 goals had been scored to that point.

However, the unpredictability continued as Brisbane reversed the trend and ran away to a sensational win.