The Reds skipper converted his first penalty before the break after Rafael handled Luis Suarez's cross inside the box, before doubling his side's advantage after a Phil Jones foul minutes into the second half.
Gerrard missed the opportunity to become the first ever Premier League player to score a hat trick of penalty kicks after Nemanja Vidic was sent off for bringing Daniel Sturridge down in the area.
The 33-year-old picked his spot for the third time of the afternoon but hit the post, although Suarez managed to add a third minutes later.
The result moves Brendan Rodgers' side up to second in the Premier League table, four points off league leader Chelsea. United, by contrast, remains seventh - 14 points off Liverpool.
An under-par performance coupled with a further dent to United's European aspirations piles more misery on David Moyes and United, as the club Merseyside rival remains firmly in the hunt for a first league title since the 1989-90 campaign.
Sturridge was quick to showcase his movement if not his finishing prowess early on when he fired wide after just two minutes before Liverpool appeals for a penalty were waved away.
Suarez appeared aggrieved after feeling the clumsy tackles of Jones and then Marouane Fellaini in quick succession warranted spot kicks - but Clattenburg had other ideas.
Other than Liverpool's early pressing, chances were few and far between in the opening exchanges - Robin van Persie's blocked effort was the best United could produce before Sturridge spurned the opportunity to test David de Gea when he failed to fashion a clean strike on goal after turning Vidic.
Allen did force the Spaniard into a save shortly after, capitalizing on Vidic's error to get an effort away on goal, before Rafael handled inside the area to give Liverpool a penalty after Suarez cut in from the left wing.
Gerrard kept his cool to send De Gea the wrong way and hand the visitors a 34th-minute lead - while Rafael will perhaps feel a touch fortunate not to have been given a second yellow card, having already been cautioned for a foul on the Liverpool skipper.
United finished the half on top, Wayne Rooney first seeing a shot saved by Simon Mignolet before the follow-up was well blocked by Martin Skrtel.
But the home side made the worst possible start to the second half when Jones bundled into Allen, with Gerrard registering 10th Premier League goal of the season with another penalty.
Gerrard was denied a hat trick when he struck the post from the spot 12 minutes from time, though the victory was complete when Suarez latched on to Sturridge's through ball to register his 25th league goal of the campaign.
- Sports & Recreation
- Luis Suarez
- Daniel Sturridge
- Nemanja Vidic
- Premier League