Defending champions Leinster and the Ospreys took two points apiece after an entertaining Pro12 draw at the RDS.
Joe Bearman and Ashley Beck crossed the line for the Welsh outfit while Dan Biggar added 17 points with the boot.
Leinster led 16-9 at the break but the Ospreys cam roaring back in the second half to take the lead.
McGrath's late try looked to have given Matt O'Connor's side the win but the Ospreys managed to work the ball into the Leinster half in the closing moments and manuafacture a penalty which Biggar converted for a share of the spoils.
The result sees Leinster remain third in the table after two games, with Ospreys moving up to fourth.