The result saw the teams swap places at the foot of the table and was a fourth defeat on the spin for newly-promoted Harworth.
Zak Khalifa gave the Steelmen a 36thÂ minute lead with a fine left foot strike into the bottom corner.
Nathan Forbes-Swindells added the second six minutes later with a good turn and finish.
ParkgateÂ wrappedÂ up the points with the third two minutes into the second half through Mark Collinson after Colliery goalkeeper Samuel Jepson had only half punched clear.
Josh Davies got one back for Harworth by curling in a fine free-kick from 20 yards just before the hour mark but it proved no more than a consolation effort.
Rossington Main extendedÂ their unbeaten run to four matches in all competitions after coming from a goal down toÂ win 2-1 at Nostell Miners Welfare, who had started the day second in Division One.
Rossington were almost gifted the lead when a poor clearance from the goalkeeper fell to Jordan Turner but his effort flew just over the crossbar.
Lee Holmes had a great chance to give Main the lead on 18 minutes but firedÂ over after Declan Howe had pulled the ball back.
However, it was Nostell who grabbed the lead five minutes before the interval. Joe Wood cutÂ in from the left and fired home.
RossingtonÂ levelled just past the hour mark when Brad Billam's cross foundÂ Howe whose well struck shot went in with the aid of a deflection.
Ryan Hindley's side were now looking the most likely winners and, after Holmes had forced another excellent save from the home goalkeeper,Â Main grabbed the decisive goalÂ with five minutes remaining.Â Holmes got it, prodding home from close range following a corner and a scramble.