Coleman caught a 16-yard touchdown pass in the first half on a halfback option by Jawan Jamison, while weakside linebacker Khaseem Greene had 22 tackles and a forced fumble, his sixth of the season.
Trent Steelman scored for Army on a 1-yard run on its opening series, but Rutgers kept the Black Knights off the board the rest of the way with its No. 4 ranked run defense limiting the nation's No. 1 ground game (375.44 yards) to 282 yards, including 86 in the second half.
The game was tied 7-7 with less than 11 minutes to play when Army self-destructed with the first of two costly mistakes in the punting game.
Punter Chris Boldt made the first one, shanking his kick 9 yards to the Army 45.
Runs of 5 and 9 yards by Jamison got the ball to the 31. Nova capped the four-play drive finding Coleman in the right corner of the end zone after the sophomore beat safety Justin Trimble for a 14-7 lead.
Army went three and out on its next series and freshman snapper Andrew Ellerson air-mailed the ball over Boldt on a play that started at the Rutgers 31. The Black Knights recovered the ball at their own 1, but it went to Rutgers on down.
After losing a yard on first down, Huggins scored from 2-yards out.
Harmon closed out the scoring with 40 seconds to go, catching a fumble by backup quarterback A.J. Schurr in mid-air and taking it to the house to cap the Scarlet Knights ninth straight win over the Black Knights, who were coming off an impressive upset of Air Force.
Army dominated the first half and left the field tied 7-7 because it had two field goals blocked, lost a fumble by Steelman in the red zone and saw receiver Chevaughn Lawrence drop a touchdown pass in the final minute.
The Black Knights outgained Rutgers 212-96, with 196 yards coming on the ground despite losing fullback Larry Dixon to an ankle injury for most of the half.
If there was anything surprising about the half, it was the Scarlet Knights' decision to only let Gary Nova throw only five times. The sophomore quarterback was intercepted six times in their last game two weeks ago, but the decision was surprising because Army didn't seem to have the personnel in the secondary to cover a group of speed.
Army took the opening kickoff and went 76 yards in 16 plays with Steelman capping the drive from a yard out. The Black Knights converted three third-down plays with the biggest being a 26-yard run by Dixon to the Rutgers 6.
Marcus Cooper blocked a 43-yard field goal attempt by David Grochowski on the Black Knights' next possession.
The Scarlet Knights tied the score early in the second quarter with a little trickery Jamison's halfback pass to Coleman at the end of an 11-play, 74-yard drive.
Army had a chance to take the lead on the next series, but Steelman (26 carries for 108 yards) fumbled at the Rutgers 11. The Black Knights still had another chance later in the half but Lawrence dropped Steelman's 13-yard pass into the end zone and Lorenzo Waters blocked a low 30-yard field goal attempt by Grochowsk.
The Black Knights have a 12-game losing streak in games played away from West Point, and they have lost 15 straight against Big East competition. They have not defeated a ranked team since knocking off Air Force in 1972.