Match Action from Petershill Park
With barely two minutes on the clock, we were ahead through Gray, who was making her first league start for City.
After initially knocking the ball towards goal with her head, an effort that was blocked, the attacking midfielder regained it at her feet and struck the ball into the bottom corner to put us ahead.
And it would be 2-0 with only five minutes played, with Harrison netting a drive into the corner from inside the area.
It could have been three by the 15-minute mark, but Hayley Lauder saw a lofted effort drop just wide of the target.
Our No.4 had a go again soon after, another strike from distance, but on this occasion it landed in the hands of Partick Thistle goalkeeper Jennifer Currie.
We would get our third, though, and it came from a stunning long-range strike by McLaughlin. From at least 20 yards out, she unleashed a rocket of a shot that soared into the back of the net.
In the second half, Harrison bagged her brace inside the opening 10 minutes when she tapped home a Lisa Evans cross, a couple of yards out from goal at the near post.
City goalkeeper Lee Gibson would be called into action when Thistle looked to bag a consolation goal, but she was alert to deny Sienna McGoldrick, when the Celtic loanee cut inside and struck a shot at goal.
It was almost a brace for McLaughlin, too, with the midfielder seeing this strike from distance come back off the crossbar.
We went so close to goal number five within the final 15 minutes, with the goalkeeper unable to deal with a cross whipped in from the right flank, and it landed to the feet of Sofia Määttä at the back post, but she hit it the wrong side of the post.
Lisa Forrest also had a good opportunity to add to our advantage, with Maddy Earl - who had come on to make her debut moments earlier - cut the ball back to the forward, but she struck her shot right at Currie in the Thistle goal.
Full-time: Glasgow City 4-0 Partick Thistle
Glasgow City goals: Gray 2, Harrison 5 and 53, McLaughlin 25
Glasgow City: Gibson; Evans, Smit (Muir), Brownlie (Golob), Warrington, Lauder, McLaughlin, Gray (Stark), Whelan (Forrest), Määttä, Harrison (Earl)
Subs not used: Clachers, Wróbel, Anderson, Thomas