And four clean sheets on the bounce have offered manager Gary McAllister further evidence that his squad is strong enough to finish in the play-offs.
No wonder he was in buoyant mood at the end of a week that had seen him handed an extended contract by chairman Ken Bates.
Jermaine Beckford's goal made him the first Leeds player to score 20 in a season since Mark Viduka in 2003. It is also twice the number reached by last season's top marksman David Healy.
Beckford suffered an ankle injury which is not thought to be serious, though it makes him a doubt for Saturday's penultimate home game of the season against second-placed Carlisle.
United could hardly have made a more impressive start at Brisbane Road. After Dougie Freedman had a goal disallowed for offside, Paul Huntington got a faint flick to Bradley Johnson's free-kick at the near post to open the scoring with just 16 minutes gone.
It was the former Newcastle defender's third goal of the season.
Home goalkeeper Glenn Morris made fine saves from Freedman and Jonny Howson before Freedman found Beckford, who scored with a left-foot volley into the top corner, five minutes into the second half.
Howson was again a driving force in United's midfield while at the back, Huntington showed once again that he will take some shifting when Rui Marques recovers from the hamstring injury that has kept him out of the last two games.
United must change their defence against Carlisle as left back Alan Sheehan starts a two-match ban but McAllister has sufficient strength in depth to cope.
The manager said: "As we go into the final push, I have people bursting to play. I have 18 or 19 players who are well capable of performing at this level ad we will be relying on them, not just the 11 who started at Orient.
"It was a very solid, professional performance with the right result. If it hadn't been for their keeper making four of five saves the scoreline could have been anything.
"We've had four clean sheets in a row and there are goals in this team. Orient have had a fantastic season, punching above their weight on occasions, but it is a real boost for us to be in the top six.
"We have five games left, there is so much to play for and the play-offs are in our own hands."
David Prutton's return after injury as a 73rd minute substitute increases competition in the midfield area.