Steele shot an 8-under 62 on Thursday morning that stood up for a one-stroke lead in the first round at TPC River Highlands.
The 31-year-old Californian opened with an eagle, holing a 129-yard wedge shot in the rain. He birdied six of the next 12 holes, and closed the bogey-free round with five straight pars.
Steele went from a long to a short putter while trying to qualify for the U.S. Open and though he missed that tournament, he said the change seems to be paying off. He needed just 26 putts Thursday.
"Speed control is a lot better," he said.
Steele finished two shots off the course record set by Patrick Cantlay in 2011 as an amateur.
"On 14, I started to think 59, which is probably why I slowed down a little bit," Steele said.
Bud Cauley and Ryan Moore shot 63, and Chad Campbell, Joe Durant, Scott Langley, Eric Axley and Jeff Maggert followed at 64.
Former Stanford stars Patrick Rodgers and Cameron Wilson made their pro debuts, with Rodgers shooting a 66, and Wilson a 73. Rodgers won 11 college tournaments and this year's Ben Hogan and Jack Nicklaus awards as the nation's top college player. Wilson won the NCAA individual title.
Two-time heart transplant recipient Erik Compton, coming off a second-place tie in the U.S. Open, had a 74.
Steele and Cauley went out in a steady rain Thursday morning, but by noon the sun had broken through.
"It took the rain pretty well," said Masters champion Bubba Watson, who shot a 67 and was among 75 players to break par. "It's kind of soft, but not too windy, so you can score around it."
But nobody could catch Steele, who had spent last week watching from the stands as his favourite hockey team, the Los Angeles Kings, won the Stanley Cup.
Cauley started on the back nine and got his round going on the signature 15th hole. He avoided the woods on the right and put his tee shot within 20 feet, then made the eagle putt.
"With that pin back right, if you hit it right, that's obviously not where you want to be, and obviously there's water left," he said. "So I hit that right where I was trying to and rolled it up there and capitalized with the putt."
Campbell was at 7 under until he hit it into the water on the same hole.
Moore, who has four top-10 finishes in eight starts at this tournament, credited his 63 to a decision not to practice after a poor round in the pro-am Wednesday.
"I was relaxed and comfortable and just went out and played golf today instead of overdoing it and over-thinking it, which I feel like I've maybe done a little lately," Moore said. "I've been practicing too much."
Trevor Immelman had the shot of the day, making a double eagle from 246 yards on the par-5 13th hole. He used a 3-wood and cleared a green-side water hazard.
"The main thing is to keep it dry," he said. "You got to get it over there, and it came out pretty good and started rolling."
Immelman also had three bogeys in his round of 68.
Defending champion Ken Duke opened with a 65.
Louis Oosthuizen withdrew after seven holes because of back issues.