Garryowen ended Cork Constitution's title ambitions with this victory at Temple Hill, but the Light Blues lost their place at the top of the table on points difference to Lansdowne.
Two penalties by Johnny Holland had the home side 6-0 ahead after 20 minutes, but a try by Roy Brosnan and a conversion and a penalty by Geoff Ryan put the visitors ahead at the break.
Con's Niall O'Driscoll and Garryowen's Ronan O'Mahony exchanged tries, before Holland and Ryan both struck penalties for their sides, but the visitors held on.
St Mary's College 16
A first-half try from Darragh Fanning proved crucial in Templeville Road, as reigning champions St Mary's College got back to winning ways with a hard-fought triumph.
Clontarf got off to a fine start when Richie Lane split the posts. Mary's hit 'Tarf with a sucker punch in the 39th minute when Fanning drove over for the opening try, converted by Steve Toal-Lennon. Penalties from Toal-Lennon and Gavin Dunne (2) sealed it for Mary's.
Young Munster 40
Old Belvedere 3
Young Munster proved too strong for Old Belvedere at Clifford Park as they maintained their challenge for honours with a bonus-point win.
Young Munster led 13-3 at half-time, No 8 Neville Melbourne crossing the line, and they dominated the second half. Tries by Lukas Kuntz and a brace by Darragh O'Neill earned their biggest win of the season, Brian Haugh kicking four penalties and four conversions.
Dolphin enjoyed a fine start with an early Rory Scannell try, but Mark Roche then crossed for Lansdowne. Cooney bagged his first try on 23 minutes, and Willie Earle added another just before the break.
Two penalties from Ronaldson, Cooney's second try and a Jordi Murphy burst put the icing on the cake for the hosts.
BALLYNAHINCH dropped their first points in the league, but Malone had to withstand some intense late pressure to share the spoils after building up a 15-0 interval advantage.
Hinch dominated most of the second half but the strong home defence only conceded two tries.
OUTHALF Stuart Olding was the hero for Belfast Harlequins in College Park, as his 15-point haul moved the Ulstermen up to fourth.
Olding notched a hard-earned five-pointer, and was also on target with a penalty and a conversion in the first half, before they saw off the Trinity challenge with a try from Matthew Holmes.