Gray signed for Watford in the summer of 2017 and even played in the Premier League for them, but upon the expiry of his contract he has been released by the Hornets.
He is officially set to leave the club this month and Preston were interested in signing the free agent this summer.
The Lilywhites were earlier in the month even claimed to be in advanced talks to bring the striker to Deepdale.
However, the striker will not be arriving at Deepdale this summer as he is now on the verge of a move to Aris Salonika, according to Greek daily Sportime.
An agreement has been reached between the parties and Gray will now travel to Greece this weekend to undergo a medical ahead of his signing for the Greek club.
Gray has played for the likes of Brentford, Burnley and Luton Town but next season will be his first sojourn out of England.
The striker spent the last season on loan with Queens Park Rangers in the Championship, where he scored ten goals, but he will not be spending the next term in the second tier with Preston.