Goals from Danny Welbeck, Adnan Januzaj and Ashley Young sealed a comprehensive victory for David Moyes' side, despite Carlton Cole's late consolation for the Hammers.
Goals from Danny Welbeck, Adnan Januzaj and Ashley Young sealed a convincing win for David Moyes' side, although Carlton Cole converted a late consolation for the Hammers.
Successive home defeats to Everton and Newcastle United ramped up the pressure on manager Moyes earlier this month but there was no repeat on this occasion as United coasted to its fourth win in a row in all competitions.
Welbeck gave the Premier League champion the lead in the 26th minute with his first league goal at Old Trafford in more than 14 months.
The England forward turned provider 10 minutes later, setting up teenager Adnan Januzaj, who took his first home goal for the club with aplomb.
United substitute Ashley Young provided the only highlight of the second half for United when he curled home his second goal in four days with 18 minutes left.
However, Cole beat the offside trap to race clear and slot through the legs of David De Gea eight minutes from time to pull one back for the Hammers, though it was too little, too late.
The result was slightly soured for United as Welbeck limped off with what looked to be a muscle injury early in the second half.
United climbed to seventh in the table with the success, while West Ham – which looked sluggish after the 2-1 Capital One Cup quarterfinal win at Tottenham on Wednesday – remains 17th.
Wayne Rooney returned from a minor groin problem for United to partner Welbeck up front but Nemanja Vidic (knock) and Marouane Fellaini (back) remained on the sidelines.
Spanish goalkeeper Adrian retained his place for West Ham while striker Modibo Maiga was promoted after scoring the winner at White Hart Lane.
Still missing suspended captain Kevin Nolan, the Hammers struggled to get a foothold in the game and only an excellent Adrian save denied Tom Cleverley from close range in the second minute.
Rooney then curled a free kick over the bar and Antonio Valencia forced a decent stop from Adrian, before United's pressure told.
A lovely flick from Welbeck released Rooney in space and he returned the pass, as the former burst into the penalty box to fire past Adrian from a tight angle.
Januzaj strolled through West Ham's defence to double United's lead nine minutes before the break. The United starlet and Welbeck linked up before the 18-year-old sold James Collins a dummy, slid past him and curled in his first ever goal at Old Trafford.
Valencia blasted over just before halftime and four minutes after the break, Jonny Evans' towering header had to be turned wide by Mark Noble.
Collins went close with a header at the other end but United were still dominant – Javier Hernandez only denied by the offside flag after scoring in the 68th minute.
But Young finally sealed the result shortly after, capping a routine win for United by curling Rooney's pass into the top-right corner.
That meant Cole's late goal had little significance as United posted a comfortable victory.