Leaders Grays dumped Scarborough on to the bottom of the Conference.
Jamie Slabber fired Grays ahead from 25 yards and battered Boro went on to collapse in the second half.
Glenn Poole hit the second with a 12-yard shot, sub Gary Hooper scored with a drive into the bottom corner and Michael Kightly knocked in the fourth.
More dismal Scarborough defending saw Paul Foot bring down Gary Hooper in the penalty area and Stuart Thurgood converted the resulting spot-kick.
Grays Athletic: Eyre, Sambrook, Nutter, Stuart, Thurgood, Angus, Martin, McLean (Kightly 59), Oli (Hooper 68), Poole (Olayinka 76), Slabber.
Subs Not Used: Bayes, Matthews.
Goals: Slabber 27, Poole 53, Hooper 69, Kightly 82, Thurgood 90 pen.
Scarborough: Walker, Lyth, Weaver, Foot, Cook, Coulson, Beadle, Bishop, Rix (Hackworth 78), Clark (Nicholson 61), Quayle (Wake 60).
Subs Not Used: Redfearn, Kelly.
Booked: Cook, Weaver.
Ref: F Graham (Essex).