Ulster 25-24 Harlequins, Kingspan Stadium
John Cooney kicked the decisive penalty in the closing stage allowing Ulster to edge out Harlequins with a 25-24 margin at Kingspan Stadium on Saturday.
The win means Ulster have climbed to the top of Pool 3 with 12 points while Harlequins are positioned third at five points.
The home side got off the mark in the eighth minute with Cooney's penalty goal but two minutes later Marcus Smith helped Harlequins level the scores with a three-pointer of his own.
The visitors seized the lead for the first time in the game when Alex Dombrandt breached the defence of Ulster to touchdown in the 25th minute and with Smith's conversion the scoreline became 3-10.
However, Ulster ensured both the teams went into the break equal when a crossfield kick from Billy Burns found Stuart McCloskey, who in turn sent Sean Reidy over the line in the 32nd minute followed by extras from Cooney.
Ulster were quick to get off the block in the second half as McCloskey found his name in the scoring sheet with a dive over the line in the 43rd minute but with Cooney failing to slot the extras the scoreline became 15-10.
Nevertheless, Harlequins dominated the end of the third quarter with back to back tries from Elia Elia in the 57th and 60th minutes and with Marcus Smith kicking both the conversions the scoreline became 15-24.
Adam McBurney provided a vital breakthrough with his try at the back of a maul while Cooney's conversion brought the gap down to two points, the scrum-half with another penalty in the 79th minute ensured Ulster registered a one-point victory.