Sean Thornton was at the heart of the action as he returned from injury for this FA Cup tie against his old club.
There was joy for the Irishman when he supplied the cross for Luke Ashworth to head Orient ahead after just six minutes.
Then six minutes into the second half it was agony when his was the final touch as Chris Shuker's shot deflected past Glenn Morris into the net.
This was an eventful round one cup tie for Thornton, and he was booed throughout by Rovers fans who still felt jilted by his departure from Prenton Park, seven years ago.
But in general this fixture rarely felt like a cup match and Orient, aside from a late flurry, clung on for the 1-1.
But now they have the chance to settle this tie at home on November 17.
Tranmere started with five at the back but had the most of the possession with Michael Ricketts as a big target man up front.
But they made nothing of it, while Orient struck with their first attack of the game.
Luke Ashworth met Sean Thornton's curling corner and headed past Rovers keeper Luke Dainels.
It was Ashworth's first ever goal for Orient. Thornton showed his delight to Rovers fan who were jeering him.
Minutes later and Morris made a great one handed save to deny Chris Shuker from 12 yards out. The ball got trapped under Ricketts' feet and the chance was gone.
The host's continued to enjoy the majority of possession, as Orient defended deep and rode their luck at times.
Morris comfortably saved John Welsh's speculative long range effort on 20 minutes.
Patulea was sometimes the sole Orient player in Rovers' half and he chased every ball which came his way.
Orient's midfield was often by-passed by the defenders who lumped long balls in the direction of McGleish and Patulea.
But when the midfield was involved, the visitor's threatened.
After neat link-up play down the right side, Ashworth drove in a low cross on 28 minutes which was just begging for someone to get a boot on it.
Thornton was a target all game, on the pitch as well as off it.
He complained to the referee after Shuker had dug his studs into his thigh on 40 minutes, and then delived another delivery into the box for Ashworth.
The way the Irishman was willing to put his foot on the ball and then look for an opening will be an asset for Orient.
Rovers threatened again on 42 minutes when Orient's defence opened up and let Shuker into the area to shoot at Morris, who was alert to his threat.
Orient looked far from comfortable as they took their one goal lead into the half-time break.
And six minutes after the re-start, Shuker hit the equaliser.
His persistence in the box against sloppy defending by Orient paid off as he let fly with a shot which deflected off Thornton and into the net.
Two minutes later Morris pulled off a marvellous reaction save to deny Ricketts at his near post.
Orient had the same problem building through the midfield as in the first half, and Rovers dominated possession.
Ben Chorley was welcomed back to Prenton Park, in contrast to Thornton. But he got booked on 71 minutes for one sliding tackle too many.
Rovers always looked the most likely to score in the second half, in due partly to Orient's absence of bite up front.
Loick Pires wide shot on 85 minutes was Orient's sole effort of the second half.
Roll on November 17 at Brisbane Road.
Full team: Morris, Purches (c), Chorley (booked 71), Ashworth, McGleish, Thornton, Demetriou, Daniels, Pires, Smith, Patulea (Jarvis 67).
Subs: Jones, Cave-Brown, Jarvis, BAker, Scowcroft, Beautyman.
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