In the 34th minute, McAlistair strode powerfully down te left flank and squared the ball to Templeman, who executed a nimble shuffle before firing low past Michael Brown from the edge of the box.
Six minutes later the tall striker repeated his smart footwork to carve out an opportunity for himself in the right-hand corner of the box, and Brown had no chance as the well-struck shot spun off Edward Forrest and looped into the net.
The third arrived two minutes later. Templeman's nimble-footedness allowed him to create the space for a sharp, low left-footed shot which beat Brown from 14 yards.
Forfar fought back ferociously after the break. David McClune clipped the bar, Mathu King headed just wide, an Edward Forrest lob was cleared off the line by Stuart McCluskey and Paul Shields hit a post.
In a rare Morton break, Templeman was fouled by David King and Peter Weatherson thumped home the penalty.
David McGurn's knees kept out Ricky Waddell's shot as the Loons roared back, but the keeper excelled himself with an outstanding save from a Tosh penalty after Alan Mahood was ridiculously penalised for bumping iinto King. Then McGurn produced a superb finger-tip save from a Barry Sellars' free-kick.