United are now in a strong position to hold off the challenge of Liverpool in the final month of the season.
They are showing their class and experience at a vital time after setbacks in March raised hopes of the title going to Merseyside.
But it now seems that it is only a matter of time before United are parading the trophy around Old Trafford once again.
There was a season's-best crowd of almost 34,000 at the Riverside Stadium that generated a terrific atmosphere at the start of the game.
Middlesbrough began with plenty of spirit but there was never any doubt of the outcome after the PFA's Player of the Year, Ryan Giggs, put United ahead midway through the first half.
Ji-Sung Park increased their lead six minutes after the break and the visitors appeared to play with plenty in reserve in the final stages of the game.
Middlesbrough, however, look set for the Championship as, once again, they had a lack of a goal threat in attack. This has been a major failing all season and manager Gareth Southgate will no doubt have a striker at the top of his shopping list in the summer.
Giggs captained United and celebrated his PFA award with a 25th-minute goal. Nemanja Vidic provided the pass and, from 20 yards, Giggs took careful aim with a left-foot shot. Brad Jones could only look on as the shot flashed into the corner of the net.
United fans were quick to taunt the home supporters with "going down, going down" chants while the Middlesbrough fans responded with "we support our local team" - a reference to their prestigious youth academy.
Middlesbrough faced a tremendous task at the start of the second half but the Giggs goal had affected their confidence and it was no surprise when Park collected a Wayne Rooney pass and left Jones helpless with a strong shot.
While United can now prepare for another league title, Middlesbrough must rebuild for the future. Chairman Steve Gibson has promised to keep faith with Southgate despite a traumatic season.
There will be, however, a player exodus with England winger Stewart Downing top of the list.