Bill Coghlan hit a half century as Clontarf eased past Leinster, while Malcolm Nofal's five-wicket haul ensured North County beat The Hills in the North Dublin derby.
Defending champions Leinster lost again as Clontarf turned in a fine all-round performance at Castle Avenue.
Obus Pienaar (3-29) and Conor Kelly (2-18) had the Rathmines side in all sorts of difficulty as they slumped to 65 for 6, and it took a 7th wicket stand of 55 between top scorer Michael Hogan (38) and Ian O'Herlihy (20) to get them up to 125 for 8.
Coghlan thumped 8 fours and a six in a fine 56 from 49 balls, while Pienaar made an unbeaten 36 from 28 balls (5 fours, 1 six) as Clontarf eased to an 8-wicket win with 15balls unused.
At Milverton, Malcolm Nofal's brilliant five-wicket haul ensured the Fingal bragging rights went to North County as they beat The Hills by 13 runs.
Chasing 132, The Hills openers Sean Terry (29) and Mark Donegan (23) got the hosts off to a steady start, but the required rate was creeping up.
Nofal struck twice to dismiss Albert van der Merwe and crucially skipper Max Sorensen without scoring.
He went one better, taking three wickets in six balls, including that of Hills' overseas debutant Daya Singh, who had threatened a comeback with a hard-hit 30 from 24 balls, to finish with the excellent analysis of 5 for 16.
Earlier, Singh had taken 3 for 28 as County made 132 for 9. Hills old boy Jonathan Andrews top scored with 42, while Eddie Richardson made a run-a-ball 31.
The Phoenix v Pembroke game is now the only outstanding league match to be refixed in the division.
LEINSTER PREMIER RESULTS
Clontarf (24) beat Leinster (1) by 8 wickets. Castle Avenue, 16 May.
Leinster 125-8 (20.0 overs, M Hogan 38, O Pienaar 3-29, C Kelly 2-18)
Clontarf 128-2 (17.3 overs, B Coghlan 56, O Pienaar 36*)
The Hills (3) lost to North County (22) by 13 runs. Milverton, 16 May.
North County 132-9 (20.0 overs, J Andrews 42, E Richardson 31, Daya Singh 3-28, A van der Merwe 2-20)
The Hills 119-8 (20.0 overs, Daya Singh 30, S Terry 29, M Nofal 5-16)