In the 2002–03 season, unavailability from Larrieu saw McCormick play five games in a row, starting with a 2–1 Football League Trophy win against Chester City.
An injury to Larrieu early in the 2003–04 season saw McCormick become first choice for the rest of the campaign, playing 43 games across all competitions, as Argyle were promoted as Champions of Division Two.
[8] On 7 June 2008, McCormick was arrested by patrol units of the Central Motorway Police Group on suspicion of causing death by dangerous driving.
McCormick's Range Rover collided with a Toyota Previa at 5.45am between junctions 15 and 16 of the southbound M6 motorway, near Keele Services in Staffordshire.
[9] Their father, Philip, the driver of the Previa, was taken to the University Hospital of North Staffordshire with fractures to the neck, back, ribs and swelling of the lungs.
[19] He played 15 matches for Oxford, but lost his first team place to Max Crocombe by mid-April and he was released at the end of the season.
[20] In May 2013, it was reported that McCormick was in talks to return to Plymouth Argyle, five years after his departure;[21] on 9 May 2013 he re-signed for the club on a one-year contract.
[22] McCormick managed to establish himself as Argyle's first choice goalkeeper ahead of Jake Cole until he fractured and dislocated a finger on his left hand in a 1–1 draw with Mansfield Town on 1 February 2014, which ruled him out for the rest of the season.
The campaign was a strong one for McCormick, as he started all 53 league and cup matches, kept 22 clean sheets and won Argyle's player of the year award.
He suffered an injury in mid-November and was deputised by James Bittner, and later Christian Walton, before finally making his return to the side on 19 December in a 2–1 away win against Hartlepool United.
[28] Argyle reached the League Two playoffs once again, this time falling to a 2–0 defeat to AFC Wimbledon in the final at Wembley, with goals scored by Lyle Taylor and Adebayo Akinfenwa.
[31] Argyle made it to the third round of the 2016-17 FA Cup with a 1–0 replay win at Newport County, thanks to an extra time goal from Graham Carey,[32] and drew Liverpool away from home.
[38] Loan keeper Steven Benda then took over goalkeeping duties, leaving McCormick to only play one more game for the rest of the season: a 1–0 EFL Trophy defeat to Bristol Rovers.
[42] "We feel Luke will provide good competition with Mike Cooper for the first-team position," said manager Ryan Lowe.
He played in Truro's 1–0 FA Trophy Qualifier win against Cirencester Town that day, replacing the suspended James Hamon.