Rob McKelvey and Nick Watney finished one shot back at 5-under-par 137. Scott Sterling, Jason Enloe and Scott Petersen followed at 4-under-par 138.
Morse played the back side first at Hershey Golf Club's East Course and picked up three birdies over his first nine holes. He then made a splash on the front nine with an eagle at the par-5 first.
'Distance always helps out here but the premium here is to hit the fairways and greens and then go from there,' said Morse. 'If you start missing greens here, they start rolling off the slopes where it's difficult to get up and down.'
The 46-year-old, who captured the PGA Tour's Hawaiian Open in 1995, added birdies at the sixth and the eighth to match the course record.
'It was a marvelous score,' said Morse. 'I didn't feel that good this morning. Hitting the ball on the range I was pretty iffy but it seemed like if I hit a good shot it turned out good and if I hit a poor shot I made a great recovery.'
Gow, a two-time winner on the Nationwide Tour, collected three birdies on the front nine before running off three consecutive birdies starting at the par-4 10th to pull ahead at 9 under.
The Australian struggled, however, with three bogeys over his last five holes to complete a round of 68.
'It's a huge advantage to know the course,' said Gow. 'The guys who are on their first time around don't know quite where to miss it. The guy who wins at the end of the week has missed the ball in the correct spot. This week is going to tell if you're playing good or not. So far, so good for me but we'll see what happens on the weekend.'
First-round leader Jason Caron struggled to a round of 73 to join Ryan Howison, Mike Springer and Ben Bates in a tie for eighth at 3-under-par 139.
The 36-hole cut came at 2-over-par 144 with 69 players surviving for the final two rounds with last week's winner Kevin Stadler making it on the number. Among those who failed to make the grade where Gavin Coles, Bubba Watson and Brad Elder.