York City hit back with two second-half goals from Darren Edmondson and Stephen Brackstone to take a precious point.
The O's looked to be on course for victory after Justin Miller fired them ahead after less than two minutes following a cross by Tom Newey - his first goal for the club.
Orient added a second 11 minutes before the break and Newey was the architect again with a cross from the left.
Top scorer Gary Alexander's header was touched onto a post by York keeper Mark Ovendale and Lee Thorpe gleefully knocked the ball into an empty net.
However, it was tough on the visitors who had chances of their own on a slippery surface.
Lee Nogan was denied by home keeper Lee Harrison after racing clean through and then Gary Browne's goalbound effort was blocked by the home defence.
But in the second half York hit back in style and just before the hour skipper Edmondson chipped home a superb effort from 20 yards after finding acres of space down the right.
Then the visitors levelled when Brackstone fired home from the edge of the area following some poor defending.
After that both sides could have won the game as Orient went close with efforts from debutante Gabriel Zakauni and Thorpe, while Dave Merris volleyed over at the other end.
After the game York's player-boss Chris Brass said: "I'm extremely happy to come away with a point after being 2-0 down at half time.
"The second 45 minutes were probably the best we have played all season. I just told the boys to be patient at half time because I knew there were goals out there." Orient's caretaker boss Martin Ling was not so happy. "It was very disappointing, we were in full control at half time and let it slip through out grasp," he said.
"We are always one result away from anything that's going on in this division."