'The greens are good and they had some pretty tough pin placements,' said Quigley, who like Tanaka is seeking his first win on the PGA Tour.
Scott Verplank, who fired a tournament-record-tying 61 in last year's final round en route to a tie for 17th, opened with a 65 on Thursday for a share of third place with Tim Herron, Briny Baird, Kaname Yokoo, Jonathan Kaye and Skip Kendall.
'I played very well actually,' said Verplank, who hit 12 of 14 fairways, 15 of 18 greens in regulation and putted 27 times Thursday. 'I finally started rolling a few putts in. I haven't been doing much of that lately and for some reason I got a little better feel today and made a few.'
Peter Lonard, 34, a three-time winner on his home circuit in Australia, is competing in his first season on the PGA Tour after tying for 10th at the 2001 Qualifying Tournament. He has yet to miss a cut in 14 events played and was well on his way to making it 15 with a bogey-free 66 in first-round action.
Alongside Lonard at 4-under par were Kirk Triplett, Steve Pate, Glen Hnatiuk, Mathew Goggin and Steve Allan.
Notah Begay III, hampered by a bad back since winning in Hartford two years ago, shot a three-under 67, just his second sub-70 round in a year in which he's missed all 11 cuts.
Begay was in 15th place with Scott Hoch, Corey Pavin, Jim Carter, Deane Pappas, Brandt Jobe and Peter Jacobsen, who captured the 1984 Greater Hartford Open, the first held at River Highlands.
Paul Azinger, the winner here in 1987 and '89, finished four shots off the pace with 10 players, among them Davis Love III, Mark Calcavecchia and Joe Durant.
Although a tournament will often have problems drawing a quality field the week following a major championship, five of the top-10 players in the world decided to make the short trip from Long Island's Bethpage State Park, site of the last week's U.S. Open, to the suburbs outside Connecticut's capital.
Phil Mickelson, the second-ranked golfer in the world and the 2001 GHO champion, turned in a 1-under 69 as he began his quest to become the first player to successfully defend this title. Also with 69s were No. 3 Ernie Els and No. 4 Sergio Garcia, while Vijay Singh, the world's eighth-ranked player, carded an even-par 70.
Seventh-ranked David Duval continued his season-long struggle on Thursday. The man who will defend his British Open title a month from now made eight bogeys in a three-over 73. Should Duval fail to qualify for the weekend after Friday's round, it would mark his fourth missed cut in his last five starts.
Quigley, 32, the nephew of current Senior Tour star Dana Quigley, was caddying for his uncle when he set the tournament record of 61 at Wethersfield Country Club in 1982. While the younger Quigley didn't enter record territory on Thursday, his 64 was his best round of the 2002 campaign.
After starting strong with four birdies over his first six holes, Quigley rolled in a 20-foot birdie at the 11th. He moved atop the leaderboard with a two-putt birdie at the par-5 13th.
Quigley made bogey out of a bunker at the 16th but returned to 6-under courtesy of an 18-foot birdie putt at 17.
'I think I've tried too hard this year. I've come out feeling like I should be able to take it to the next level,' said Quigley, who registered his best showing on the PGA Tour when he finished second at last year's Greater Greensboro Classic. 'As a result, I think I've tried too hard, and certainly the last few months it's been pretty frustrating.'
Quigley missed seven cuts and was disqualified once, at Bay Hill, in his first 11 starts of 2002. Although he missed only one cut over his next six events, Quigley's highest finish in that span was a tie for 30th in Greensboro.
Tanaka, who has 15 victories worldwide, including 10 on the Japan Golf Tour, hit all 14 fairways and took just 25 putts in the first round.
'I didn't have too many big mistakes, and my putts and my shots were very good,' the 31-year-old Tanaka said through an interpreter.
The purse for the event was increased by a healthy $900,000 from last year to $4 million. The winner will take home $720,000.
Full Field Scores from the Canon Greater Hartford Open
PGA Tour Statistics