The Rockets limited the Wizards to 39 percent shooting from the field, marking just the second time this season Houston has kept its opponent below 40 percent.
"We just take too many tough, bad shots in situations sometimes," Washington coach Randy Wittman said. "You have to move the ball and we don't and that gets us in trouble and we fall in a hole."
After the Wizards scored the first two points, Houston didn't trail until a brief spell midway through the third quarter. Harden hit a 3-pointer with less than seven minutes left in the third, giving Houston a one-point lead, and the Rockets never trailed again.
Beal hit a 3 with one minute remaining in the first half to tie the game at 40. The Wizards trailed by as many as 14 in the first half before going on a 9-0 run late in the second quarter.
Toney Douglas hit a 3-pointer from beyond the half-court line as time expired in the second to put the Rockets up 45-42 at the break.
Jordan Crawford started at point for Washington, while A.J. Price remained out with a fractured right hand suffered last Saturday against Golden State. John Wall has missed the entire season with a stress injury in his left knee.
The Wizards also played without Trevor Ariza, who strained his left calf last Tuesday against Miami, and Trevor Booker (right knee), who started the first six games.
Notes: Chris Singleton had a career-high four blocks for Washington. ... Greg Smith and Patrick Patterson both registered a season-high three blocks. ... Houston C Omer Asik had 16 rebounds, recording double-digit rebounds for the second straight game and sixth time in his last nine outings.