Nicklas Bendtner fired a hat-trick as Arsenal recovered from their League Cup Final loss to Birmingham City in a one-sided fifth-round replay against Orient to set up a titanic quarter-final against Manchester United.
The Gunners' victory was never in doubt after Marouane Chamakh and Bendtner put Arsenal 2-0 up and Arsene Wenger's side bounced back emphatically from Sunday's shock defeat by Birmningham.
Manchester City also reached the last eight with an easy win over much-changed Aston Villa team and they face Championship side Reading who beat Premier League Everton on Tuesday.
"It was important we came back from Sunday's defeat with a win," Arsenal manager Arsene Wenger told reporters.
"We are having a fine run apart from Sunday's defeat which came under special circumstances. But we played very well tonight."
The Gunners, held to a 1-1 draw by third tier Orient in the first game, were looking for a rapid response after Sunday's painful 2-1 loss when they conceded a last-minute goal to Birmingham after a mix-up between goalkeeper Wojciech Szczesny and defender Laurent Koscielny.
But there were no mistakes at Emirates Stadium where the crowd were subdued until Arsenal took control of the game.
Chamakh settled nerves with a well-taken side-footed goal, his first since November, after seven minutes before Bendtner headed the second, Arsenal's 100th of the season in all competitions.
Orient, who scored in the last minute to take the tie to a replay, had chances in the opening stages with Dean Cox almost cancelling out Arsenal's opener after 14 minutes.
But despite a spirited performance from the visitors, Arsenal were too sharp and had too much guile, and that included 19-year-old midfielder Conor Henderson who had a fine debut.
Bendtner's second just before half-time exposed the gulf in class between the teams when he beat off defenders before firing a curling shot past goalkeeper Jamie Jones.
Jones had no chance of saving his 62nd-minute penalty either before Gael Clichy wrapped up the win with an angled left-foot drive 15 minutes from time.
EARLY GRIP
Manchester City took an early grip at Eastlands with Yaya Toure opening the scoring after Villa failed to clear a corner in the fifth minute.
The ball bounced off the shoulder of Ciaran Clark and into Toure's path and he cracked it home from inside the six-yard box.
Mario Balotelli, beginning to settle at City after a difficult first few months at Eastlands disrupted by injury, added the second when he collected a pass from Toure and sidefooted home a half-volley from 15-metres that bounced in off Brad Friedel's post.
David Silva added the third 20 minutes from time with a powerful drive from the edge of the penalty area.
The other quarter-finals are Stoke City against West Ham United and Birmingham against Bolton Wanderers.
