Farnborough found themselves a goal up after six minutes when Anthony Charles pulled down Robert Traynor and Jay Smith curled a wonderfully executed strike over the wall and into Scott Tynan's bottom right-hand corner.
But the early goal only seemed to spur Barnet on. In the 14th minute Grazioli pounced on a Jake Cole error to roll the ball into the empty net.
He followed it up with a delightful lob, and a side-footed finish completed his hat-trick.
In between Richard Graham hit Barnet's third to leave Farnborough totally shell-shocked at the interval.
Boro boss Neil Sillett made three changes at half-time and the risk back-fired when Cole was involved in a head-on collision with substitute Lee Roach in the 67th minute. The 19-year-old keeper had to be stretchered off.
Having used up all of their substitutes, left-back Jimmy Turner found himself between the sticks. After Tony Taggart's was sent off for two bookings Farnborough were always fighting a losing battle.
Turner was finally beaten when substitute Damien Batt drove home following good work by Roach. Roach and Dean Sinclair completed the rout late on.
Barnet took full advantage of Boro's lack of discipline which was compounded by Kevin Hemsley's late dismissal for a professional foul.
The Bees now look odds-on to achieve promotion after completing their third victory in a row. This was Farnborough's fourth defeat on the spin and they are running out of time to save their Conference place.