The Blues were out of the blocks quick in the first half and defender Hannah Doherty exploited the space afforded to her by the Glens defence to put Linfield ahead.
Just before half-time Amy McAlister went on to make it 2-0 to the south Belfast side.
Glentoran came out a different side in the second half and looked certain to get back into the game only for the Blues keeper Nicole Adams to save a penalty from Gail Macklin.
With 15 minutes left Glentoran's Kelly Bailey scored a cracking 35 yard free-kick and the comeback was on.
In the dying seconds the Glens made sure the points were shared with sub Rebecca Bassett poking home a corner to level the tie.
Glens midfielder Nadene Caldwell said her side were determined to get a win following a dire first half.
She said: "We didn't come out for the first half and Linfield put us under pressure and their goals only spurred them on.
"We knew we had to come out in the second half and change things and we knew we had to get the draw or the win and obviously we would have preferred the win."
Linfield manager Ryan McConville added: "We were the best side in the first half, but Glentoran went to the very end and got their equaliser right on the stroke of full-time which was very disappointing, but credit to them for not giving up."
Elsewhere Shankill United Predators were no match for Cliftonville Ladies who took all three points in a 4-1 win.
While Crusaders Strikers and Ballymena United Allstars played out a scoreless draw.
That result puts Crusaders tied third with Cliftonville in the league.