The home side thought they had done enough to secure the points as they held a two-goal advantage with ten minutes remaining.
But Bo’ness showed their characteristic grit and determination to hit back and maintain their unbeaten start to the league campaign.
United started brightly but couldn’t capitalise and Penicuik opened the scoring in the 35th minute albeit slightly against the run of play.
Andy Forbes ran onto a Callum Connolly diagonal and sent a cross in which deceived everyone and crossed the line after coming off the post, despite the best efforts of Andy Murphy and Ross Campbell to clear.
Bo’ness were rattled and let in another goal five minutes later. Craig Stevenson swung in a harmless looking free-kick into the area which the Bo’ness defence stood watching thinking it was going out of play, Arron Ponton however was alert to the error and cut back the ball from the touchline to Connolly who had the simple task of tapping in from close range.
Right on half-time Bo’ness thought they had pulled a goal back, but Campbell’s acrobatic effort was ruled off thanks to an offside flag.
Bo’ness boss Max Christie switched things up at half-time and they soon pulled a goal back when Brian Morgan headed a Tom Grant corner home.
Penicuik were undaunted by the setback and there was a good response from the home side. Scott McRory-Irving was inches over with a drive from 25 yards and Sam Jones also threatened from distance without troubling Murphy.
Penicuik increased their lead from the penalty spot after a trip on Sean Stewart in the area. Craig Stevenson took responsibility and coolly sent Murphy the wrong way and the two goal advantage was restored.
With around ten minutes remaining Bo’ness grabbed what looked to be a consolation goal back thanks to Craig Comrie’s deflected strike.
And they levelled at the death when Keast found the net with a driven cross-cum-shot which flew over Robert Watt and into the top corner.