Allenby won for the second time on the PGA Tour this season, cruising to a three-shot victory at the Marconi Pennsylvania Classic in Ligonier.
The 30-year-old Australian collected $594,000 and moves over the $2 million mark in seasonal earnings.
'I don't think I could have hit it any better,' said Allenby. 'I felt so comfortable with my swing. This is the first time I've felt this good.'
Larry Mize (65) and Laurel Valley course member Rocco Mediate (68) tied for second place at 16-under.
Mize had not finished higher than 35th all year. He made a 12-foot birdie putt on the final hole to earn a share of second place and $290,400.
The 1987 Masters champion finally moves into the top-125 on the money list and is in good shape to maintain his Tour card for next season.
This is Allenbys fifth top-5 finish in the last two years on the PGA Tour ' four of which have resulted in victory.
This is also his second straight multiple-win season in the states. Last year, he claimed victory in the Shell Houston Open and the Advil Western Open.
Both of his 2000 triumphs came in playoffs, as did his win earlier this year at the Nissan Open.
Such sudden-death measures were not needed this week.
Allenby took control of the weather-plagued tournament by shooting a second-round 65, which came over the course of two days.
He continued his scoring ways by playing the first seven holes of his third round in 5-under-par.
When play was suspended due to darkness Saturday night, Allenby held tight to a two-shot lead over local favorite Mediate. He then came out Sunday morning and added another stroke to his advantage with a birdie on the par-4 16th.
Allenby led by three entering Sunday afternoons final round ' and no one would get any closer.
The Aussie recorded six birdies and two bogeys en route to shooting 4-under-par 68, and finishing the tournament at 19-under 269 ' a new 72-hole record for the second-year event.
Full-field scores from the Marconi Pennsylvania Classic