KUALA LUMPUR, 5 Feb 2015 (AFP) - The Englishman handled the breezy conditions at the Kuala Lumpur Golf and Country Club and putted confidently en route to seven birdies on a course where he thrives.
"It was a good start and I'll take that. I putted nicely and started the ball on the line well," he said.
Westwood, who has won the tournament twice before, pulled away from the field last year to win by seven strokes. He said this week the course is one "where I almost feel like a member".
McDowell, the former US Open champion kept the pace, also notching seven birdies against a single bogey on the demanding course.
"It's tough to pinpoint what you have to do right on this course because you have to do everything right," he said.
England's Tommy Fleetwood was a stroke off the lead, tied with Malaysia's Danny Chia and Sunghoon Kang of South Korea.
Europe's victorious Ryder Cup captain Paul McGinley was among several golfers on three-under 69.
The Asian Tour's current top-ranked golfer David Lipsky of the United States is among the expected contenders who stumbled out of the gates.
Lipsky had three bogeys and a double to finish on an even-par 72.
France's rising star Victor Dubuisson was expected to mount a challenge to Westwood but pulled out before play started, citing illness.
Kuala Lumpur, Malaysia | AFP | Thursday 2/5/2015 - 11:46 GMT | 118 words
Scores after Thursday's first-round of the $3 million Malaysian Open at Kuala Lumpur Golf and Country Club (par 72):
66 - Lee Westwood (ENG), Graeme McDowell (NIR)
67 - Tommy Fleetwood (ENG), Danny Chia (MAS), Kang Sung-hoon (KOR)
68 - Alejandro Canizares (ESP), Anders Hansen (DEN), Prom Meesawat (THA)
69 - Richard T.Lee (CAN), Paul McGinley (IRL), Andrew Dodt (AUS), Jake Higginbottom (AUS), Paul Waring (ENG), Stephen Gallacher (SCO)
70 - Mohamad Iylia Jamil (MAS), Robert Karlsson (SWE), Gregory Bourdy (FRA), Anirban Lahiri (IND), Andy Sullivan (ENG), Felipe Aguilar (CHI), Romain Wattel (FRA), Robert Rock (ENG), Marc Warren (SCO), Scott Barr(AUS), Alvaro Quiros (ESP), Nicolas Colsaerts (BEL), Peter Hedblom (SWE), Bernd Wiesberger (AUT), Emilliano Grillo (ARG)