The highlight of a dominant opening 40 minutes from 'Quins was a sublime solo try from speedster Fiyin Olayisade who left the Crescent defence for dead and coasted over from his right wing berth.
Flanker Andrew Gillespie and impressive loosehead Tim Morton grabbed tries as the hosts built up a 19-6 half-time lead. Ulster out-half Niall O'Connor kicked two conversions.
Crescent, whoses first half points came from two Mark Woods penalties, fell further behind when blindside Tamaiti Horua, another member of the Ulster squad, broke free for a 46th minute try.
The Limerick men hit back with an unconverted effort from Woods and while former Crescent captain Phil Glamuzina collected a late five-pointer, 'Quins had the final say when their skipper Robert Logan crashed over from close range, allowing O'Connor to convert and extend the winning margin to 15 points.
Bruff also made an impressive start to their AIB League campaign, securing a bonus point with a 40-8 dismissal of hosts Highfield at Woodleigh Park.
Eoin Cahill's side were full value for their win, taking a stranglehold on proceedings from the outset when winger John Moore was worked in for a lovely try.
League debutant Patrick Thompson made a sixth minute break, splitting the Highfield defence before linking with full-back Brendan Deady whose flicked pass put Moore over in the corner.
Bruff skipper Brian Cahill was off target with his conversion attempt but kicked two penalties to one from Highfield's Colin Mahony, moving his side into a 11-3 lead.
The Limerick outfit added a converted try on the stroke of half-time, taking advantage of a Highfield sin-binning to pressure the home pack into the concession of a penalty try.
A huge drive was finished off with flanker John Stephen Shine dotting down, early in the second half, and Bruff's bonus point was secured by a superb Nigel Riordan score.
On as a replacement for out-half Tony Cahill, Riordan took the ball on 40 metres out, breaking out of a succession of tackles and dashing through for his first AIB League try, which Brian Cahill converted.
It was becoming a rout as centre Gary Leonard (62 minutes) and replacement lock Graham Bolger (71) helped themselves to tries.
Bruff had to finish the game down to 13 men - Alan Bourke and Brian Cahill went off injured after the bench had been emptied - and Highfield gained some consolation with an injury-time try from Frenchman Mike Bayssat.
In Saturday's local derby at Donnybrook, a powerful Lansdowne side emerged victorious on a 42-9 scoreline.
Old Wesley, winners of the Division 3 play-off title last May, were very much second best on the day and could only muster three penalty goals from David Smith.
The work done on the training pitch with head coach Willie Clancy, forwards coach Aidan McCullen and backs coach Gordon D'Arcy came to fruition as Lansdowne put down a marker for the rest of the campaign.
Playing into a stiff wind, the visitors led 18-9 at the break thanks to tries from Healy and Paddy Flood and eight points from the boot of Andrew Geraghty.
Using their territorial dominance to eke out further scores in the second half, Healy, Ross McCarron and Brian O'Riordan crossed the Wesley whitewash and a penalty try took Lansdowne's try tally to a handsome six.
At College Park, former Leinster out-half David McAllister kicked 16 points (three penalties, two conversions and a drop goal) as Terenure College got the better of Dublin University in a hard-fought capital clash.
'Nure, coached this season by Ian Morgan, led by 19-17 at half-time and had to dig deep to see out a 26-20 win.
Thomond registered a 34-6 bonus point win over Greystones at Liam Fitzgerald Park, a result which will give the Limerickmen great hope for the league run.
Having led 13-6 at the break with Warren Kelly getting an early try, they piled on the points in the second half with further touchdowns from Brian Buckley, Declan Cusack and captain Ed Fraher. Barry Lynn kicked two penalties for Greystones.
Cusack put in an excellent afternoon's work for Thomond, finishing with a personal haul of 16 points.
Elsewhere, Niall Smullen and Ronan McCabe were amongst De La Salle Palmerston's six try scorers as they enjoyed a 38-14 triumph over Clonakilty at Kirwan Park.
Playing in their first match back in Division 2, UCD proved too strong for Galway outfit Corinthians as they cantered to a 36-7 win.
Out-half Niall Earls, a former Youths international, finished as top scorer, bagging a try, four conversions and a penalty.
Influential flanker Kevin Croke and backs John Cooney, Michael Twomey, Andrew Cummiskey and Terry Jones were the students' other try scorers, while hooker Dave Barden touched down in the second half for Corinthians.
Bective Rangers' trip to Belfast was a fruitful one as they beat Malone 24-10 at Gibson Park, lively scrum half Dave Campbell and winger Michael South scoring the Dubliners' tries.
AIB LEAGUE DIVISION 2 RESULTS: Saturday, October 3
Belfast Harlequins 31 Old Crescent 16, Deramore Park
De La Salle Palmerston 38 Clonakilty 14, Kilternan
Dublin University 20 Terenure College 26, College Park
Highfield 8 Bruff 40, Woodleigh Park
Malone 10 Bective Rangers 24, Gibson Park
Old Wesley 9 Lansdowne 42, Donnybrook
Thomond 34 Greystones 6, Liam Fitzgerald Park
UCD 36 Corinthians 7, Belfield