The 33-year-old Aucklander beat top seed and world No20 Ryan Cuskelly, of Australia, in five games in the semifinals and then won the title in four games over Scotsman lan Clyne.
Grayson won 11-5, 11-9, 9-11, 11-7 to continue his unbeaten run of results against Clyne in what has been a good year after he won the Irish Open title in April.
"I'd been in the semis and finals of a few tournaments this big, but hadn't won one. I'm stoked to win it. Alan [Clyne] is always tough and also to have beaten Ryan as well. I used good tactics to win that one.
"Winning this title has been great to start the season along with earlier in the year taking out the Irish Open and I did well at the British Open too, although I was a bit angry at the way I played in the nationals final against Paul [Coll, New Zealand No1] and thought I could have offered more in that match.''
The win in Houston was his 14th career title. He now has a block of training leading up to a busy period with a PSA tournament in San Francisco, followed by the US Open in Philadelphia.
Grayson, who has competed at four Commonwealth Games, has a world ranking of 43 and should improve to around the 35 mark which is close to his high of 32 achieved early last year.
