The former Bolton Wanderers youth, a late first-half substitute, hammered in a vital header just after the hour mark to secure another huge three points for the champions-elect.
A failure by Robbie Neilson’s side to beat Ayr United this Friday evening would now set-up a potential title-clincher for County with a win then needed at home to Partick Thistle to seal a Premiership return.
It was no night for the purists as Dunfermline put in a dominant first-half display, only to succumb to a County revival after the break.
County looked flat through much of the first half, with the Fifers forcing the best of the chances.
On-loan Aberdeen striker Bruce Anderson snapped at the heels of the home defence early on and forced a strong block from Dutchman Kenny van der Weg after only six minutes.
When Van der Weg sent a clearance straight to Dunfermline’s Matthew Todd soon after, the Pars wide man thrashed in a first-time shot, with Scott Fox tipping it over the bar.
Approaching the half hour, Todd was unlucky to rattle the upright with a 15-yard snapshot while, a couple of minutes later, James Craigen curled a 20-yard attempt around the outside of the County post.
County managed only one minor incursion with Josh Mullin’s ferocious low cross forcing defender Danny Devine to stab a foot at it to re-direct over his own bar.
The hosts’ already depleted squad suffered another potential blow on half-time as Van der Weg hurt his leg stretching for the ball and exited.
After a lame first half, County re-emerged a different side.
Michael Gardyne’s rocketed attempt was parried over the bar by Pars keeper Ryan Scully after a foray on the left and, moments later, Brian Graham’s header spun wide.
Jamie Lindsay, scorer of a dramatic leveller against Dundee United on Friday night, was next to tear forward and drive a stinging shot against the gloves of Scully.
The raised energy and tempo continued with Gardyne’s hanging cross from the left met close in by the raised leg of Graham, but parried to safety by the keeper.
County’s reward came just after the hour. Mullin’s corner from the left swirled to the edge of the six-yard box and there was young centre-half Grivosti to bulge the net with a thumping header. Rather than rest on it, County tore forward again – and bedlam ensued. From another Mullin corner, Faissal El Bakhtaoui somehow cleared off the line from Ross Stewart’s header.
Graham was then denied by Scully’s block and referee Don Robertson waved away howls for a County penalty when Stewart tumbled.
A searing breakaway by Gardyne and Mullin ended with the latter denied by the legs of Scully.
The Pars couldn’t muster much of worth as County held out comfortably