Leaders Leinster came from 10 points down to secure a draw as Glasgow Warriors squandered a chance to consolidate themselves in fourth spot.
Glasgow broke the deadlock through Ruaridh Jackson's 29th-minute penalty.
Warriors extended their lead with a 46th-minute penalty try that Jackson converted, with Isa Nacewa yellow carded for the visitors.
But Heinke van der Merwe's try, converted by Ian Madigan, and a late Nacewa penalty levelled the scores.
Glasgow's fourth draw of the campaign meant they missed the opportunity of completing the double this season over the Irish side.
The Dubliners had racked up 17 wins and a draw since the Warriors left the RDS celebrating a 23-19 victory in September and the late penalty stretched that unbeaten run.
Leinster were first to pass up an opportunity in a very uninspiring first half at rain-drenched Firhill, fly-half Madigan striking the upright with an early penalty attempt.
The hosts opted not to kick at goal from penalty awards on two separate occasions in the opening 10 minutes and had to wait until the 28-minute mark for another opportunity.
A long punt from full-back Peter Murchie was gathered by Madigan, who spilled that ball under pressure from the onrushing home defence.
The resulting scrum was collapsed by the Leinster front row, allowing Jackson to notch the game's first score.
Madigan was again off target moments later when he skewed another effort wide.
Fiji full-back Nacewa took over the kicking duties from Madigan as the half reached its close, yet a slip in his run-up ensured his penalty did not threaten the scoreboard.
Glasgow began the second half with a degree of urgency that had been lacking in the first period and their increased aggression created the first clear try-scoring opportunity.
Captain Rob Harley secured scrappy lineout ball and beat one defender before slipping the ball to the onrushing Pat MacArthur, who charged toward the corner.
The last-ditch covering tackle of Nacewa appeared to have diverted MacArthur into touch just inches short of the line, only for referee John Lacey to award a penalty try, deeming Nacewa's tackle to have been dangerous play.
Jackson gratefully nudged over the conversion from beneath the posts as the Fijian was sent to the sin-bin.
Yet, just as Glasgow appeared to have gained the initiative, Leinster hit back thanks to a try from prop Van der Merwe, who bundled over after a spell of forward pressure, Madigan slotting the conversion.
Having returned from the sin-bin, Nacewa was restored to kicking duties and it was his calmly-struck penalty effort 10 minutes from time that earned Leinster a share of the spoils.
Glasgow: Murchie, Lemi, Dunbar, Nathan, Shaw, Jackson, Pyrgos, R. Grant, MacArthur, Welsh, Campbell, Ryder, Harley, Fusaro, Wilson. Replacements: Seymour for Lemi (67), Aramburu for Nathan (63), White for Jackson (67), Reid for R. Grant (63), Hall for MacArthur (56), Verbakel for Campbell (30). Not Used: Hunter, Forrester.
Leinster: Tries: van der Merwe. Cons: Madigan. Pens: Nacewa. Leinster: Nacewa, D. Kearney, Macken, O'Shea, Carr, Madigan, Boss, van der Merwe, Strauss, White, Browne, Flanagan, Ryan, Jennings, Auva'a. Replacements: O'Malley for O'Shea (41), Conway for Carr (63), Hagan for White (58), Toner for Flanagan (41), Murphy for Ryan (66). Not Used: Dundon, J. McGrath, Cooney.
Ref: John Lacey (Ireland).