A Graham Rusk goal gave UCD a shock 1-0 win over league leaders Sligo Rovers at the UCD Bowl to end the westerners’ unbeaten start to the season.
The only goal of the game came on 29 minutes when striker Rusk met Danny Ledwith superb cross to head past Gary Rogers.
Second-placed St. Patrick’s Athletic failed to take advantage, however, as their unbeaten start also came to an end as they were stunned in losing 2-1 at home to lowly Dundalk.
Mark Griffin earned ten man Dundalk their win at Richmond Park as he levelled Chris Forrester’s first half opener on 78 minutes before then hitting a stoppage time winner.
Dundalk had had midfielder Michael Rafter sent off in the tunnel at half-time.
Champions Shamrock Rovers could only draw 0-0 at bottom side Monaghan United, though they edged a point ahead of St. Patrick's into second place in the table, seven points behind Sligo.
A 90th minute winner from Ryan McEvoy gave Bohemians a 2-1 win over Shelbourne in the Dublin derby at Tolka Park.
Shels had midfielder John Sullivan sent off on 33 minutes, but went in a goal up at the break from a Glenn Cronin penalty.
Peter McMahon levelled for Bohs from a bizarre overhead kick in the 53rd minute before McEvoy volleyed home his late winner.
Derry City came from behind to beat Bray Wanderers 3-2 at the Brandywell to make it three wins on the spin.
Kieran Waters gave Bray the lead two minutes before the break.
But winger Stephen McLaughlin scored twice inside seven minutes just past the hour mark to appear to put Derry in command.
In a cracking contest, Danny O'Connor drew Bray level on 72 minutes before Ryan McBride won it for Derry four minutes later when heading home a corner.
Daryl Horgan kept Cork City's good run going as he hit the equaliser to earn Tommy Dunne's side a 1-1 draw at Drogheda United.
Declan O'Brien punished poor defending to shoot Drogheda into a 27th minute lead.
Horgan hit back for City eleven minutes into the second half when availing of a goalkeeping error by Gabriel Sava to level and make it five games unbeaten for the Leesiders.