Harlequins made hard work of a victory that ought to have been more emphatic given their possession and Newcastle’s indiscipline.
Newcastle put themselves under enormous pressure, playing 30 minutes of the 80 with 14 men after having three players sin-binned in the course of an hour. Harlequins went into the game knowing they needed a victory on the back of last week's first win at Leicester in 13 years to retain a strong chance of making the LV= Cup knockout stages.
Quins gave debuts to scrum-half Dave Moore and blindside Maurie Fa'asavalu, while referee David Rose wasted no time stamping his authority on proceedings, sin-binning Newcastle scrum-half Micky Young for hands in a ruck in only the second minute.
Quins wasted no time capitalising on facing 14 men. Wing Sam Smith kept his composure to steer the ball over the line with his boot before pouncing for the try, Rory Clegg converting.
Newcastle were fortunate not to fall further behind when Clegg tried to chip the defence and score on his own when he had men out wide available.
It took the visitors 18 minutes to threaten the Harlequins' defence, and they were rewarded with their first penalty, but fly-half Jeremy Manning fired wide. Their next visit to the 22 brought richer pickings as flanker Redford Pennycook spun off the back of a ruck, broke two tackles and ploughed over. Manning's conversion tied the scores.
Harlequins lost fly-half Clegg on 20 minutes, carried from the pitch on a stretcher and wearing a protective neck brace. He was replaced by Ben Urdapiletta.
Newcastle soon found themselves back under pressure and referee Rose flashed his yellow card again on 26 minutes, this time binning Pennycook for killing the ball. Urdapiletta stepped up and steered the resulting penalty high between the posts.
Quins increased their lead on the half-hour when the pack drove number eight Chris York over on the left. Manning reduced the arrears with a 36th-minute penalty and made further inroads with another penalty on the stroke of half-time.
Quins went back on the offensive from the restart and, having run one early penalty only to throw a forward pass, Urdapiletta made amends on 45 minutes with a successful shot at goal.
Newcastle came under sustained pressure on their line and, after awarding two penalties for scrum offences, referee Rose lost patience when the visitors conceded a third and gave a penalty try, converted by Urdapiletta.
Just when they looked in danger of losing touch, Newcastle hit back with a try that owed everything to poor defence. Young made an unhindered break through the heart of the home defence before arming Charlie Amesbury to score behind the posts. Manning converted.
Newcastle captain Tim Swinson became the third player sin-binned when he was sent packing on 61 minutes for tackling a player while airborne in a lineout. Urdapiletta made no mistake with the penalty.