A travelling Quins side scored four tries and picked up two bonus points from a tricky trip to Welford Road.
It was a fast start from the side’s hosts with Leicester scoring two unanswered tries within the first ten minutes from internationals Matt Scott and Ellie Genge. Both scores were converted by England stand-off George Ford.
Harlequins struck back with an unconverted Nathan Earle try immediately after Genge’s score, but soon conceded a third try via hooker Tom Youngs from an ever-impressive Tigers maul in the 19th minute.
Quins replied in lightning fashion once more, earning a penalty try in the 24th minute as Leicester prop Dan Cole was sent to the sin bin for illegal play at the Quins set-piece.
Leicester were temporarily down to thirteen men during the first half as try-scorer Genge joined Cole on the sidelines for a high hit on Quins openside Jack Kennningham, but were also the next side to claim further points as Ford kicked his first penalty of the day.
Further heartache came for Quins in the dying seconds of the first half as Leicester picked up their fourth, bonus-point securing score as Genge claimed his second try of the day after returning to the field alongside Cole. With Ford sliding his conversion wide, the Tigers held a 29-12 lead at the break.
Fired up from a half-time debrief with the coaching staff, Quins came out with the bit between their teeth in the second half, conceding just six points and scoring three tries.
After Ford slotted his 43rd minute penalty, man of the moment Marcus Smith sent a cross-field kick to centre-come-wing Joe Marchant, with the England international dotting down in the 53rd minute.
Less than half an hour to play Quins struck again through centre Luke Northmore, but not before Leicester’s reserve fly-half Zach Henry added another three to Leicester’s tally to take the home side to 35 points for the day. After Northmore’s unconverted score, Quins trailed Leicester by just six points with four minutes to go and everything to play for at 35-29.
Quins kicked off to Leicester, but were fast in recovering possession. Refusing to go quietly into the night, Harlequins pushed up-field and into Leicester’s half, with the promise of yet another dramatic win for the men in the Quarters.
In promising field position, Quins' hearts were broken by a final minute penalty at the breakdown, with Leicester’s reserve wing Kini Murimurivalu latching on to the ball to win the crucial final play of the game.