Bargoed made it 16 games unbeaten in the SWALEC Championship, running in six tries in a 34-12 win at Llanharan on January 31.
The first try came from a scrum called by Bargoed from a penalty five metres out, with number eight Ross Coombes controlling the ball at his feet to score.
The referee’s patience with constant penalties faded when Llanharan flanker Rory Martin-Smith was sin-binned just as the game entered the second quarter.
Prosser kicked to touch and a planned move saw big second row Geraint Edmonds in midfield to smash over for Bargoed’s second. Prosser converted to make it 12-0.
Two minutes later wing Lewis Protheroe crossed in the corner before Llanharan responded with a try by hooker Nathan Huish.
Bargoed rounded off the half with the bonus-point try and Geraint Edmonds’ second score of the match.
The start of the second half was scrappy and it was clear that both sides were having difficulty with the conditions. Darren Humphries got a yellow card for a deliberate knock-on but Llanharan could not make the extra man count.
Bargoed broke the second-half deadlock when prop Kieron Brown ran in from 20 metres after hitting the line at a great angle.
They extended their lead with a well worked Lee Pearson try, before Llanharan scored a cracker at the death with full back Rhys Morgan finishing off a fine passage of play.
The bonus-point win puts Bargoed 19 points above Swansea at the top and only a disaster will stop them winning the league with ten games to go.
They play bottom side Tondu at home on February 7 at 2.30pm.