Russell Slade celebrated four years in charge of the O's with a point at Bramall Lane though will perhaps be disappointed it was not two more after his side let slip a lead against his former club.
Dean Cox gave Orient the lead before the interval with a cool touch and finish but an improved United drew level in the second period after the lively Jamie Murphy found space to run behind the O's.
The O’s boss shuffled his pack and went with a 4-3-3 formation with Kevin Lisbie leading a forward trident that included Moses Odubajo and Dean Cox.
It was a strikingly attacking bench for the travelling side which boasted four strikers as David Mooney took up a spot alongside Shaun Batt, Chris Dagnall and Robbie Simpson.
The formation seemed to suit the O’s who looked fluid in the opening exchanges with Lloyd James anchoring the midfield three behind John Lundstram and Jamie Ness.
Despite that, the opening quarter of the match passed relatively incident free as both sides knocked the ball about neatly without penetrating either defensive line.
Chris Porter was the target man for each Blades attack as he tussled with Nathan Clarke and Mathieu Baudry and helped to craft a couple of chances for the lively Ryan Flynn though he failed to test Jamie Jones in the O’s goal.
At the other end Ness hit the wall with a free-kick from a good area and Odubajo fizzed a dangerous cross along the face of the goal but no one was able to get on the end of it as both goalkeepers awaited their first save.
The O’s were patient in possession as the half ticked on and worked the ball well in tight areas to frustrate their opponents but it was just in the final third where they at times lacked a bit of invention to unlock the Blades defence.
The home side looked intent on working the ball into wide areas and Jamie Jones had to be alert to parry a John Brayford cross to safety with 10 minutes of the half remaining.
But with the half drawing to a close the O’s broke the deadlock with Cox grabbing his 13th goal of the season. Odubajo was the creator with a run across the Blades back four and after Lundstram kept the ball alive with a well won header, Cox showed great skill and composure to lob the ball over his marker and prod a finish past Mark Howard to send the O’s into the break ahead.
Perhaps the home side had one eye on the FA Cup semi-final with Hull at Wembley next week, but their supporters seemed frustrated at the lack of intensity to the Blades’ performance as Orient seemed to have more time on the ball, though early in the second period, Conor Coady seemed intent on changing that as he forced Baudry into a mistake and led to Cox bringing him down to avert the danger with the winger receiving a yellow card for his troubles.
His determination seemed to encourage his teammates in red and white as they looked more at the races and soon got their leveller when Jamie Murphy got beyond the O’s back line to latch on to a long ball and keep his cool to round Jones and slot home.
Five minutes later Jones had to be alert to tip a Coady drive over the bar and with 20 minutes remaining, Slade brought Mooney on for Cox in an attempt to seize back the initiative.
It was a straight swap as the O’s stuck to their shape and the introduction of the leading marksman seemed to have an instant impact as he linked well to win back-to-back corners.
Shaun Batt also entered the fray as the O's went back to a 4-4-2 and he also seemed to give Orient life with his marauding runs alongside Lisbie who himself almost scored one of the goals of the season when he collected a long ball from Ness in Dennis Bergkamp fashion to bring it on to his right foot before his shot was charged down.
With three strikers on the field, it certainly was not a case of shutting up shop for a point as both sides smelt a winner in the dying stages but it remained level in what was probably a fair reflection of the balance of play.
Sheff Utd: Howard, Brayford, Maguire, Flynn, Doyle (C), Porter (Davies 62), McGinn (Scougall 58), Collins, Coady, Murphy, Freeman (Harris 76)
Subs: Hill, Paynter, Long, Dimaio
Goals: Murphy (63)
Bookings: Maguire (44)
Orient: Jones, Omozusi, Cuthbert, Baudry, Cox (Mooney 70), James (Batt 82), Lisbie, Odubajo, Clarke (C), Lundstram, Ness
Subs: Sawyer, Larkins, Gorman, Dagnall, Simpson
Goals: Cox (41)
Bookings: Cox (52) Odubajo (79)
Referee: Michael Jones
Attendance: 16,809 (677)