You can wield a quarterstaff as either a two-handed or one-handed weapon.
Benefit: By employing a number of different stances and techniques, you can wield a quarterstaff as a one-handed weapon. At the start of your turn, you decide whether or not you are going to wield the quarterstaff as a one-handed or two-handed weapon. When you wield it as a one-handed weapon, your other hand is free, and you cannot use the staff as a double weapon. You can take the feat Weapon Specialization in the quarterstaff even if you have no levels in fighter.
Pathfinder Roleplaying Game Ultimate Magic. © 2011, Paizo Publishing, LLC; Authors: Jason Bulmahn, Tim Hitchcock, Colin McComb, Rob McCreary, Jason Nelson, Stephen Radney-MacFarland, Sean K Reynolds, Owen K.C. Stephens, and Russ Taylor.