Westbrook, who now has three triple-doubles this season, posted 20 points, 11 rebounds and 10 assists in the Thunder's season high-tying seventh straight win.
Serge Ibaka supplied 23 points with 10 rebounds and three blocks, while Enes Kanter added 15 points with five rebounds for Oklahoma City.
Ibaka canned a 3-pointer late in the first to cap a 7-0 burst for a 13-point Thunder lead, helping them take a 30-20 edge into the second.
Indiana trailed by as many as 15 in the second, but it went on an 11-2 run to cut the deficit to six. Miles' jumper just before the half pulled the Pacers within 48-42 at the break.
Oklahoma City maintained its edge in the third, but Indiana kept it close until the closing minutes. Westbrook converted a layup with 3:20 remaining to start a 12-4 quarter-ending run to stretch the Thunder's lead to 80-69 entering the fourth.
The Thunder continued their momentum at the beginning of the fourth, as D.J. Augustin connected with a 3-pointer prior to Anthony Morrow and Dion Waiters dialing in from deep and extending the margin to 20.
OKC has won 12 of its last 13 at home ... Waiters and Morrow scored 14 and 12 points, respectively ... Roy Hibbert had a team-high 10 rebounds for Indiana ... The Thunder went 16-of-18 from the line, while Indiana made 7-of-11 free throws ... OKC outrebounded the Pacers 57-48.