Johnson Wagner led throughout to win his first PGA Tour victory at the Shell Houston Open.

Wagner shot a final-round 71 to finish at 16 under and defeat Chad Campbell and Geoff Ogilvy by two strokes.

Billy Mayfair - in his 600th Tour event - and Fred Couples finished tied for fourth, the latter achieving his highest finish since a tie for third at the 2006 Masters.

Wagner received an automatic invitation to this week's Masters.

"I can't believe I'm playing Augusta," he said.

"It's a dream come true."

Wagner began the final day with a one-stroke lead and extended it to three when he made a 27-foot birdie putt - and Campbell missed a five-footer to save par on number two.

The lead grew to five strokes as Wagner continued to fare well and Campbell endured a disastrous front nine.

Wagner's lead dwindled on the back nine but he held off the challenge as the pack closed - and Campbell recovered his composure.

Padraig Harrington's 26th-place finish in Houston means he is up into an automatic Ryder Cup qualifying position.

Collated final round scores & totals in the USPGA Tour Shell Houston Open, Redstone GC, Houston, Texas, United States of America

(USA unless stated, par 72):

272 Johnson Wagner 63 69 69 71

274 Chad Campbell 73 64 65 72, Geoff Ogilvy (Aus) 67 73 66 68

275 Billy Mayfair 72 68 69 66, Fred Couples 73 69 67 66

276 Charley Hoffman 65 70 69 72, Bob Estes 71 69 64 72

278 Pat Perez 69 73 72 64, Kevin Sutherland 70 70 71 67, Jason Day (Aus) 73 71 69 65

279 Steve Stricker 66 76 66 71, Bart Bryant 69 74 66 70, KJ Choi (Kor) 74 66 69 70

280 Aaron Baddeley (Aus) 72 72 65 71, Lucas Glover 69 69 70 72, Jeff Quinney 72 68 70 70, Ryan Armour 73 69 67 71, Steve Elkington (Aus) 67 74 69 70, Kevin Streelman 72 69 70 69

281 Dean Wilson 67 75 70 69, Ben Crane 74 65 70 72, Mathew Goggin (Aus) 71 64 72 74

282 Phil Mickelson 72 68 71 71, Rodney Pampling (Aus) 70 72 68 72, Stuart Appleby (Aus) 70 70 72 70

283 John Merrick 71 69 72 71, Davis Love III 69 72 69 73, Joe Ogilvie 74 68 70 71, Kevin Na 76 68 68 71, Jose-Maria Olazabal (Spa) 69 70 73 71, J J Henry 69 72 71 71, Shaun Micheel 71 72 71 69, Padraig Harrington (Irl) 71 73 71 68

284 Robert Allenby (Aus) 75 68 69 72, Anders Hansen (Den) 69 71 75 69, Chez Reavie 70 71 70 73

285 Scott Sterling 70 71 73 71, Nicholas Thompson 69 70 78 68

286 Jeev Milkha Singh (Ind) 73 70 72 71, Justin Leonard 68 76 71 71, Omar Uresti 68 76 69 73, Tim Herron 72 70 72 72, Fredrik Jacobson (Swe) 72 72 72 70, John Riegger 71 70 69 76, Kenneth Ferrie (Eng) 75 69 71 71, Frank Lickliter II 75 67 72 72

287 Jeff Overton 71 71 69 76, Marco Dawson 72 72 70 73, Mark Hensby (Aus) 70 74 73 70, Ben Curtis 69 72 72 74, J.L. Lewis 72 72 72 71, Tim Wilkinson (Nzl) 73 69 71 74, Charles Howell III 71 72 71 73, Michael Allen 72 71 70 74, Craig Kanada 70 71 73 73, Briny Baird 67 77 73 70

288 Michael Sim (Aus) 72 72 70 74, Martin Laird 69 71 74 74, Bubba Watson 68 72 74 74, Stephen Leaney (Aus) 72 71 73 72, Harrison Frazar 72 69 76 71

289 Charlie Wi (Kor) 71 69 77 72, Robert Garrigus 71 67 75 76, Craig Barlow 70 74 71 74, Shane Bertsch 72 69 75 73

290 Nathan Green (Aus) 74 70 72 74, Stephen Marino 71 73 72 74, Brett Quigley 68 72 68 82, Yong-eun Yang (Kor) 71 73 73 73

293 Brett Wetterich 73 70 72 78

295 Carl Pettersson (Swe) 70 74 73 78

297 Justin Bolli 74 70 75 78