Lee Holmes netted for just the second time this season when he curled in from 20 yards after six minutes before the 25-year-old crossed for the impressive Hayhurst to add a second goal.
The 19-year-old academy product had previously scored in the draws with Swindon and MK Dons but his header ensured Grayson got off to a winning start at Deepdale.
And after taking maximum points from his first home game as manager, Grayson insisted he could not have asked for more from his new side.
"Will's probably thinking goalscoring is easy but we've told him to get in the right areas and he gambled today and it was the right time," said Grayson.
"I don't think I could ask much more - two goals, a clean sheet, limiting Stevenage to very few opportunities and coming out of the traps quickly.
"We asked the players to change play quickly to lead to opportunities to score goals and that worked.
"We've challenged the players to see if we can go on a run and remain unbeaten until the end of the season. It's within the grasp of the team to go do that, it might be difficult but we want to finish the season with positive momentum ready for next year."
Grayson added: "It was a great atmosphere from the supporters but it's a two-way thing, the players have got to show the supporters passion and desire too.
"I came here to achieve something. Other club's in League One couldn't match my ambitions but this one possibly can do that."