The striker, who moved from Halifax this summer, popped up with the scores level at 1-1 to put his side back into the lead.
"It's good to get off the mark," Gregory said. "It was nice to get 90 minutes under my belt but I'm feeling a bit stiff, though I'm sure I'll feel fitter for it in the next game."
The Lions had taken the lead against the Conference side through Scott McDonald, who headed in Lee Martin's cross in the 10th minute.
A mistake from goalkeeper Stephen Bywater let Aldershot straight back into the match and after Gregory converted Jermaine Easter's pass from four yards, Josh Wright curled in a superb third to make it 3-1.