The young winger spent the second half of last season at the Northern Commercials Stadium at Valley Parade, making ten appearances and helping the Bantams to reach the League One play-off final at Wembley.
He has signed a six-month loan deal with Stuart McCall's side.
Gilliead - who has been capped by England at under-16, under-17, under-18 and under-20 level - has previously spent time on loan with Carlisle United and Luton Town.
The Shotley Bridge-born 21-year-old was presented with the Jack Hixon Trophy by Alan Shearer in March 2012.
He could now line up against Newcastle when Rafa Benítez's side travel to Bradford for a pre-season friendly on Wednesday, 26th July.