Harden tallied 14 points in the third period, taking the baton from Trevor Ariza to steer the Rockets (15-4) to a 24-point advantage in the quarter. Ariza, held scoreless in the first half, had 13 points by the 6:37 mark of the third, with his first 3-pointer giving Houston a 66-63 lead.
When Ariza closed his individual spurt with a corner 3-pointer, the Rockets led 77-67. Houston stretched its advantage to 23 points early in the fourth to complete a 45-point turnaround.
Michael Beasley paced the Knicks (10-9) with a season-high 30 points while Kyle O'Quinn added a double-double of 20 points and 15 rebounds. Beasley and O'Quinn were subbing on the frontline for injured starters Kristaps Porzingis and Enes Kanter, both out with back woes.
Beasley and Courtney Lee were instrumental in the Knicks' first-quarter blitz, combining for 32 points on 13-for-16 shooting as New York dashed to a 29-7 lead on the fourth consecutive Beasley basket with 4:36 left in the first.
The Rockets, behind their bench, began a slow climb back starting at the end of the frame, with Luc Mbah a Moute, Ryan Anderson and Eric Gordon drilling four 3-pointers as the first came to a conclusion, cutting the deficit to 10.
By the intermission, Houston reserves had 30 points on 11-for-18 shooting.
As the non-Beasley Knicks cooled the Rockets kept chipping away at the deficit, finally pulling even at 51-51 on a pair of Chris Paul free throws with 3:08 left in the half.
Houston opened the second half with a 13-2 run and the Knicks, playing the second game of a back-to-back, ran out of steam.
The Rockets beat the Knicks for the 24th time in the last 26 meetings 24, and recorded their 11th season sweep over the last 13 years.
NOTES: With C Enes Kanter (back spasms) sidelined for a second consecutive game, the Knicks were also without F Kristaps Porzingis (lower back tightness). Porzingis also missed the second game of a back-to-back on Nov. 8 at Orlando. ... Rockets F Ryan Anderson (illness) and G Eric Gordon (calf) rejoined the rotation, marking just the second time this season Houston had its nine primary rotation players available. ... Rockets G James Harden became just the fourth player since the 1990-91 season to score 20-plus points in each of his team's first 19 games.