'It was a great start to my first Western Open,' said Gossett, 23, who reeled in his first PGA Tour title as a rookie at last year's John Deere Classic in Silvis, Ill. 'All in all, it was a great day's work on Independence Day.'
A total of 50 players will have a bit more work to do to complete the first round, which was delayed for nearly 3 1/2 hours because of heavy rain and lightning. Play restarted when the weather cleared but was later called for the day due to darkness. First-round action is scheduled to resume Friday at 8 AM ET.
Jerry Kelly and 1998 Western Open winner Joe Durant were at 5-under with three holes to play.
England's Luke Donald, who played his college golf at nearby Northwestern University, was one of six players in the clubhouse at 68. Six others were also hovering at 4-under, including Vijay Singh and reigning PGA champion David Toms, who made it through 16 holes Thursday.
Gossett started at Cog Hill's 10th hole and holed a 25-foot putt at the 11th for his first birdie. Though he immediately gave the stroke back after hitting his tee shot into a greenside bunker at the par-3 12th, Gossett soon surged to 3-under with a run of three straight birdies. He sank birdie putts of 12, 15 and 20 feet on the 14th, 15th and 16th holes, respectively.
Gossett hit an 8-iron to three feet to set up a birdie at the first, then birdied the third after nearly holing his approach with a wedge. He managed to reach the par-5 fifth hole in two with a 6-iron but missed his 10-footer for eagle. After tapping in for a birdie that took him to 6-under, Gossett picked up another shot with a 4-iron to six feet at the par-3 sixth.
The University of Texas product suffered his second bogey at the seventh, where he drove into a fairway bunker before three-putting from about 45 feet.
But Gossett made it a sweep of the four par-5s with a birdie at the ninth. He decided to lay up, then wedged his third shot to four feet and sank the putt.
'I've probably played this course 10 times,' Gossett explained. 'My uncle lives in Westmont, and I came up here and played the U.S. Amateur in '97, missed the cut.'
He also missed a few cuts this season, six in the span of nine events from mid-February to early May, to be exact. He mixed in a few poor finishes when he did make it to the weekend, but in his most recent start at last month's Buick Classic, Gossett tied for second for the third top-10 finish of his young career.
'The first half of the season I didn't have any great tournaments, but I learned so much,' he said. 'I'm really pleased with the way I'm playing right now.'
Estes, who earned his fourth win on the PGA Tour at last month's Kemper Open, tallied three birdies on each nine on Thursday. He rolled in an eight-footer on his final hole, the ninth, just as play was being stopped.
'It's nice to finish up the round and keep it like it normally is,' he said.
Love was 1-over par after bogeying his fifth hole, the 14th, but quickly picked up two strokes with an eagle on the 15th. He added a birdie after making the turn, then made three more over his last four holes in the failing light.
'There was some holes I could have birdied that I didn't, but I stayed patient and got a couple birdies coming in,' said Love. 'Seemed like when we started playing faster trying to get it in, we all played a little better.'
Robert Allenby, who beat two-time Western Open champion Nick Price in a playoff in 2000, carded a 3-under 69. Price shot a 1-over 73.
Defending champion Scott Hoch finished at even-par 72.
Full-field scores from the Advil Western Open