Ian Atkins' pre-match comments that there could be an emphatic end to Oxford United's abysmal home League record in midweek matches fell on deaf ears at the Kassam Stadium.
A win would have given them a second double in four days following the 3-2 win over Torquay United and end a losing run under floodlights going back to September 1998 but for most of the game they were given a lesson by Orient who were sharper and more accurate in their passing.
Matthew Brazier tested United keeper Andy Woodman with a fierce low drive after five minutes and as Orient surged forward it came as no surprise when they went ahead 12 minutes later.
Full back Matthew Lockwood sent over an inch-perfect cross from the left to Chris Tate whose header left Woodman helpless.
A magnificent save by Orient keeper Glen Morris from a Steve Basham header after 28 minutes signalled an Oxford revival and after Morris saved well from Dave Savage, Basham drove widely over the bar from Oxford's best chance six minutes before the interval.
Oxford started the second period slowly as they did in the first half and Orient, beaten 2-1 at Brisbane Road in September, doubled their lead after 54 minutes.
Brazier made a long run on the left and crossed to an unmarked Andy Harris who headed in his second goal in 134 games.
Atkins sent on three substitutes for the last 30 minutes but United were so disorganised against a solid defence that the Londoners were never in danger of conceding a goal.
The defeat lessened Oxford's chances of competing in the play-offs and more worrying is that two of their next three matches at the Kassam Stadium are on Tuesday evenings.
The Londoners' win pleased manager Paul Brush. "It was a good team performance against a side that could have moved into the top three if they had won," he said.
"We pushed them back from the start, made things happen and it worked for us tonight."