Allenby completed the final nine holes of his second round Saturday morning to take a one-shot lead into the afternoon.
The Australian then added to his advantage by playing 15 holes in 5-under-par to move to 14-under for the tournament, two shots clear of his nearest opponent when darkness suspended the third round.
Rocco Mediate, who is a member at the Laurel Valley Golf Club, is also 5-under through 15 holes of his third round. He stands at 12-under.
Kevin Sutherland completed his third round, and did so in just 64 strokes. Hes currently three back at 11-under.
Mediate and Steve Flesch led at 7-under as play was suspended Friday night. When play resumed Saturday morning, Allenby surged into the top spot thanks to precise iron play.
I dont recall hitting a bad shot, said Allenby, who won this years Nissan Open in a six-man playoff.
If I could have holed some more puttsI had six putts inside 10 feet. I had that on nearly every hole.
Nonetheless, Allenby shot 4-under 32 over the final nine holes of his second round and kept the scoring going in Round 3.
He birdied five of his first seven holes to take a three-shot cushion at 14-under. But Mediate carded six birdies of his own in the third round to stay within two shots.
Four players are tied for fourth place at 10-under. Cameron Beckman and Jay Haas shot 65 and 66, respectively, in the third round. Nick Price and Steve Elkington and each through 16 holes.
Flesch is now nine off the pace after playing the first nine holes of his third round in 4-over-par 40.
Marconi Pennsylvania Classic