CASTELLON, October 20, 2011 - McGowan, who is down at 543 in the world and battling to save his card, hit a seven under par 64, a round highlighted by an eagle two at the 503-yard 17th and five birdies.
"It's nice to be playing well again and up in contention," said McGowan, whose hopes of a Ryder Cup spot last year were scuppered by a wrist injury.
"I'm just trying to play each shot at a time and put up a good result at the end of the week. It’s nice to shoot 64. It looks like my game is getting better. I’m looking forward for tomorrow morning."
McGowan is two in front of Richard McEvoy and Paraguay's Fabrizio Zanotti, and three clear of a group which includes Sergio Garcia and Northern Irishman Michael Hoey on his first appearance since winning the Alfred Dunhill Links Championship title.
Defending champion Matteo Manassero, the 18-year-old Italian, had to settle for a 69 after kicking off with four successive birdies, while 20-year-old Lewis, winner of the Portugal Masters in only his third professional start on Sunday, shot 71.
The English youngster was suffering from a virus and turned in a disappointing three over, then had four birdies in a row, but closed with another bogey.
Colin Montgomerie had one birdie for a 70, while playing partner John Daly finished with back-to-back double bogeys for a 73.
Leading and selected first round scores in the European Tour Castello Masters at the Club de Campo del Mediterraneo, Castellon on Thursday (GBR and IRL unless stated, par 71):
64 - Ross McGowan
66 - Richard McEvoy, Fabrizio Zanotti (PAR)
67 - Anthony Wall, Gary Orr, Sergio Garcia (ESP), Danny Willett, George Coetzee (RSA), Thongchai Jaidee (THA), Michael Hoey
68 - Thomas Aiken (RSA), Niclas Fasth (SWE), Robert Coles, Marcel Siem (GER), Steven O'Hara, Mark Foster
69 - Damien McGrane, James Kingston (RSA), Scott Strange (AUS), Matteo Manassero (ITA), Maarten Lafeber (NED), Mark Brown (NZL), Ricardo Gonzalez (ARG), Alexander Noren (SWE), Gonzalo Fdez-Castano (ESP), Gregory Havret (FRA)
70 - Carlos Del Moral (ESP), Scott Jamieson, Anthony Kang (USA), Gary Boyd, Alejandro Canizares (ESP), Marcus Fraser (AUS), Jeppe Huldahl (DEN), Colin Montgomerie, Matthew Zions (AUS), Brett Rumford (AUS), Carl Suneson (ESP), David Drysdale, Romain Wattel (FRA), Matt Haines, Richard Green (AUS), Gregory Bourdy (FRA), Lorenzo Gagli (ITA)
71 - Christian Cevaer (FRA), John Parry, Christian Nilsson (SWE), Floris De Vries (NED), Magnus A Carlsson (SWE), Joost Luiten (NED), Johan Edfors (SWE), Felipe Aguilar (CHI), Tom Lewis, Stephen Gallacher, Michael Jonzon (SWE), Keith Horne (RSA), Ignacio Garrido (ESP), Rafael Cabrera Bello (ESP), Thomas Levet (FRA)
Selected:
72 - Jose-Maria Olazabal (ESP), Hennie Otto (RSA), Shiv Kapur (IND)
73 - John Daly (USA)
75 - Daniel Gaunt (AUS)