McCullough won for the first time in 178 starts on the senior circuit last year in Puebla, Mexico. The now 56-year-old fired three straight rounds of 4-under-par 68 at the La Vista Country Club to win by one shot over Jim Colbert, who shot a second-round 62, and Bob Eastwood.
McCullough's victory was not only his first on the Senior Tour, but it was his first in 612 PGA Tour-sanctioned events ' 401 on the PGA Tour and 33 on the Buy.Com Tour.
After all the trouble to finally break through, McCullough collected victory No. 2 just four starts later in the Emerald Coast Classic.
The Ohio native will have to defend his title at a different venue. This years event will be contested at the par-72 Club de Golf Chapultepec in Mexico City.
The purse is $1.5 million, with $225,000 going to the winner.
Hubert Green won the inaugural event in 2000 by a smooth five strokes. McCulloughs win was much more closely contested.
McCullough trailed playing companions Colbert and Eastwood by one shot heading to the 53rd hole. McCullough sank a 12-foot birdie putt, while Colbert and Eastwood each made bogey.
Now leading by one with one hole to play, McCullough nailed a four-foot par putt at the last for victory.
Full field and tee times