LONDON, May 31, 2012 (AFP) - Slattery carded a 66 at Walton Heath three days ago to earn a US Open debut and the 33-year-old looked brim full of confidence as he scored four under par 67 to take a one-shot lead over Marcel Siem.
A stiff wind and fast-running conditions made life tough on the course where Europe beat America two years ago in the Ryder Cup.
Slattery has been regarded as a journeyman for much of his career, but he has been in fine form since last October when, on his 183rd start, he captured the Madrid Masters.
Now he looks a strong contender for Wales Open glory as he plans for a trip to San Francisco for his first US Open.
"I know Olympic Club is going to be difficult, but I'm really looking forward to it," he said.
"It's more the atmosphere. I remember The Open at Hoylake (his only previous major was there in 2006) and I thrived on it."
Slattery's round was not without its scary moments. He was an inch from going in the water on the short third and was relieved to find his ball in bounds at the 580-yard ninth.
The hole still cost him his only dropped shot, but he added: "It was very difficult. The wind was stronger than anticipated and if you get round without a bogey it's an amazing achievement."
Scotland's Paul Lawrie, second on the Ryder Cup points table, needed to birdie two of his last three holes for a 74, the same as Colin Montgomerie, while Jose Maria Olazabal took 76.
Reigning Wales Open champion Alex Noren hit an 81 before withdrawing with back trouble.
Collated first round scores in the European Tour Wales Open at Celtic Manor (GBR and IRL unless stated, par 71):
67 - Lee Slattery
68 - Tim Sluiter (NED), Marcel Siem (GER)
69 - Joel Sjoholm (SWE), Simon Thornton, Gonzalo Fdez-Castano (ESP), Pablo Larrazabal (ESP)
70 - Ross Fisher, Fabrizio Zanotti (PAR), Steven O'Hara, Marcus Fraser (AUS)
71 - Damien McGrane, Richie Ramsay, David Horsey, Richard McEvoy, George Coetzee (RSA), Thongchai Jaidee (THA), Jamie Elson, Thomas Bjorn (DEN), Fredrik Andersson Hed (SWE)
72 - Chris Wood, Joakim Lagergren (SWE), Jaco Van Zyl (RSA), Peter Lawrie, David Drysdale, Andrew Marshall, Paul McGinley, Mark Foster, Bradley Dredge
73 - Robert Coles, Oliver Wilson, Steen Tinning (DEN), Rhys Pugh, Jose Manuel Lara (ESP), Emiliano Grillo (ARG), Benjamin Hebert (FRA), Michael Campbell (NZL), Gareth Maybin, David Howell, Julien Guerrier (FRA), David Lynn, Ricardo Gonzalez (ARG), Romain Wattel (FRA), Thorbjorn Olesen (DEN), Richard Sterne (RSA), Ross McGowan
74 - Francesco Molinari (ITA), Jean-Baptiste Gonnet (FRA), Soren Kjeldsen (DEN), Joost Luiten (NED), Colin Montgomerie, Maarten Lafeber (NED), Brett Rumford (AUS), Tom Lewis, Knut Borsheim (NOR), David Dixon, Paul Lawrie, Niclas Fasth (SWE), Gregory Bourdy (FRA), Reinier Saxton (NED)
75 - Andrew Johnston, Carlos Del Moral (ESP), George Murray, Mikko Ilonen (FIN), Phillip Price, Rhys Davies, Andrew Dodt (AUS), Julien Quesne (FRA), Simon Khan, Marc Warren, Tommy Fleetwood, Ignacio Garrido (ESP), Bernd Wiesberger (AUT), Michael Hoey, Gregory Havret (FRA)
76 - Jeev Milkha Singh (IND), Peter Whiteford, Matteo Manassero (ITA), Matthew Zions (AUS), Edouard Dubois (FRA), Oliver Fisher, Raphael Jacquelin (FRA), Scott Jamieson, Jose-Maria Olazabal (ESP), Mark F Haastrup (DEN), Andrea Pavan (ITA), Miguel Angel Jimenez (ESP), Markus Brier (AUT), Richard Green (AUS), Alejandro Canizares (ESP)
77 - John Parry, Gary Orr, Anders Hansen (DEN), James Kingston (RSA), Rhys Enoch, Johan Edfors (SWE), Sam Little, Edoardo Molinari (ITA), Christian Cevaer (FRA), Alex Haindl (RSA), Richard Bland, Steve Webster, Magnus A Carlsson (SWE), Matthew Baldwin, Richard Wallis, James Morrison, Stephen Gallacher, Richard Finch, Rich Beem (USA), Lorenzo Gagli (ITA)
78 - Jamie Moul, Christian Nilsson (SWE), Jorge Campillo (ESP), Danny Willett, Peter Hedblom (SWE), Darren Fichardt (RSA), Shiv Shankar Prasad Chowrasia (IND), Oscar Floren (SWE), Daniel Denison, Andy Sullivan, Michael Jonzon (SWE), Thomas Levet (FRA)