Brandt Snedeker birdied two of his final four holes to grab the lead after the first round of the Houston Open while Shane Lowry and Graeme McDowell had a decent start to the last tournament before next week's Masters.

Lowry and McDowell both signed for round on 69, leaving them on -1 and four shots behind the overnight leader.

Padraig Harrington finished at +1 with bogeys on the 14th and 18th costing him, while Dustin Johnson, Jordan Spieth and Brooks Koepka all struggled.

Snedeker, who won the 2012 FedEx Cup, feasted on Memorial Park's par fives, nailing birdies on all three of them behind some pinpoint accuracy off the tee to card a five-under 65 to sit two strokes ahead of six players.

"This course is a long, tough golf course, so to play well you need to take advantage of the scoring holes, which I did a great job of today," he said.

The American said he was boosted by the fans in attendance. The tournament is the second to allow a limited number of fans to attend since golf came back from its Covid-19 shutdown in June.

"It's great to hear some claps and people excited for good shots and some birdies," said Snedeker, who is seeking his 10th career win on the Tour.

"That's a big reason why I think I played well. I was excited to be out there and (had) been missing them, so glad to have them back."

World number one Johnson, playing in his first tournament since testing positive for the disease and spending 11 days in isolation, had a stretch of three consecutive bogeys before making the turn and was forced to settle for a round of two-over 72.

Former world number one Spieth, seeking his first win since the 2017 British Open, went out in the morning wave and held a share of the lead through 12 holes before making two bogeys and two double-bogeys en route to a three-over 73.

Spieth's playing partner Koepka mixed three birdies with three bogeys and one double bogey for a round of two-over 72.

"I hit it terrible today," four-time major winner Koepka said.

"It's funny because I've hit it so good the last couple weeks and so that was disappointing."

The round was called for darkness with a handful of players left to complete their final holes.