You can get the Lumberjack outfit in OSRS mainly through Temple Trekking. The usual method is to unlock Temple Trekking by completing In Aid of the Myreque , then run the Burgh de Rott trek and look for the bridge event where undead lumberjacks spawn and drop outfit pieces.

Fast method

  • Start Temple Trekking in Burgh de Rott after finishing the required quest.
  • Pick Route 1 so you can skip more encounters and reach the right event faster.
  • When you get the broken bridge event with no trees , kill undead lumberjacks until a piece drops.
  • After you get one piece, leave and start a new trek, since you can’t get multiple pieces in the same event.

Helpful setup

  • Bring a weapon, food, and weight-reducing gear like Graceful.
  • A teleport back to Burgh de Rott helps a lot, especially Morytania legs 3/4 if you have them.
  • Some guides also suggest a hammer, knife, and a teleport out for awkward events.

Extra note

There is also a Forestry source mentioned in newer guides, but Temple Trekking is still the standard fast way people use for the outfit. The set gives a Woodcutting XP bonus, with the full set giving the largest bonus.

TL;DR

Complete In Aid of the Myreque , go to Temple Trekking , choose Route 1 , and farm the broken bridge with undead lumberjacks until you get all four pieces.