Leinster fought back from a half-time deficit to secure a draw in a tense Celtic League tie at Donnybrook.
Leinster (3) 16
Pens: O'Meara (3)
Ospreys (10) 16
Try: S Williams
Pens: Henson (3)
Dave Tiueti created a first-half try for Wales wing Shane Williams, and Gavin Henson's kicking built a strong position for the visitors.
But a second-half Jimmy Norton try and 11 points from the boot of Brian O'Meara meant honours were shared.
The Ospreys were left four points clear of the Blues in the battle for the final Welsh Heineken Cup spot.
Pre-kick-off injuries to Ireland backs Girvan Dempsey and Brian O'Driscoll (calf strain) disrupted the pattern of the home side early on.
The Ospreys took the lead in the 12th minute as Tiueti cut loose and looped well for Williams to run over, completing a 30-metre move.
Henson converted and added a difficult penalty in first-half injury time.
Leinster's only score of the first period came on 18 minutes when Gordon D'Arcy, back at centre to cover for O'Driscoll, was impeded.
O'Meara kicked the resulting straight penalty from 25 metres.
The game turned on its head two minutes into the second half with a high challenge by prop Duncan Jones on D'Arcy.
The centre was forced off injured, while Jones was sent for 10 minutes in the cooler.
O'Meara kicked the penalty and added the extras to a Shane Horgan-inspired try from
full-back Norton on 47 minutes.
Henson levelled matters just past the hour as he claimed his second penalty of the night.
The full-back exchanged penalties with O'Meara on 69 and 73 minutes, and Leinster number eight Victor Costello, making his 100th provincial appearance, blocked Henson's drop-goal attempt with two minutes remaining.
Leinster: G Dempsey; G D'Arcy, B O'Driscoll, D Quinlan, B Burke; F Contepomi, B O'Meara; R Corrigan (capt), S Byrne, P Coyle, M O'Kelly, B Gissing, D Dillon, N Ronan, V Costello.
Replacements: E Byrne, G Hickey, L Cullen, A McCullen, B O'Riordan, S Horgan, J McWeeney.
Ospreys: G Henson; S Terblanche, J Storey, D Tiueti, S Williams; S Connor, A Williams; D Jones, B Williams (capt), A Jones, A Newman, L Tait, J Thomas, R Pugh, J Bater.
Replacements: R Wells, A Durston, E Seveali'i, H Bennett, P James, N Bonner-Evans, S Tandy.
Referee: M Changleng (Scotland).