The striker's first goal for Leeds earned the club a 1-1 draw at Blundell Park as Grimsby threatened to protect a scoreline which belied a sizeable gulf in experience and reputation between the teams.
United's line-up included trialist Amdy Faye, who gave a steady if unremarkable debut in his defensive midfield role, but the 33-year-old was not the only recognisable face on display.
McCormack, Adam Clayton and Davide Somma were asked to stretch their limbs ahead of Saturday's Championship game against Swansea City, watched by Leeds' entire coaching staff.
Somma came as close as anyone to opening the scoring before half-time with a low shot which Grimsby's Nathan Dean blocked, and the goalkeeper reacted well to dive at the feet of Mike Grella and prevent him from converting the rebound.
The hosts did take the lead seven minutes after the break when Nathan Dixon ran clear of Lewis Turner and buried a shot with the help of a post but McCormack's close-range header restored parity.
Leeds Reserves: Paulat-Brigg, Crowe, Bromby, L Turner, White, Robinson, Faye, Clayton, McCormack, Somma (Hatfield 46), Grella.
Subs (not used): N Turner, Payne, Booker, Taylor.
United's line-up included trialist Amdy Faye, who gave a steady if unremarkable debut in his defensive midfield role, but the 33-year-old was not the only recognisable face on display.
McCormack, Adam Clayton and Davide Somma were asked to stretch their limbs ahead of Saturday's Championship game against Swansea City, watched by Leeds' entire coaching staff.
Somma came as close as anyone to opening the scoring before half-time with a low shot which Grimsby's Nathan Dean blocked, and the goalkeeper reacted well to dive at the feet of Mike Grella and prevent him from converting the rebound.
The hosts did take the lead seven minutes after the break when Nathan Dixon ran clear of Lewis Turner and buried a shot with the help of a post but McCormack's close-range header restored parity.
Leeds Reserves: Paulat-Brigg, Crowe, Bromby, L Turner, White, Robinson, Faye, Clayton, McCormack, Somma (Hatfield 46), Grella.
Subs (not used): N Turner, Payne, Booker, Taylor.