First featuring for his county at senior level under the management of Rory Gallagher, McCormick was 19 years of age then.[9] He was named on the bench for the 2017 Ulster Senior Football Championship game against Antrim.[10] In 2019, he was tipped for a return to the county senior squad.[11]Declan Bonner called him up again for the county ahead of the 2020 season.[9][12]
Alongside Termon teammate Nathan McElwaine, he played for London in the 2022 National Football League.[13] He scored 1–2 in London's opening game victory over Carlow.[14] He made his championship debut for London against Leitrim later that year.[15]
^Ferry, Ryan (10 February 2022). "McElwaine eager to impress with the Exiles". Donegal News. Retrieved 10 February 2022. 'Enda (McCormick) has been up with the Donegal seniors before and he's a good scorer. All the teams seem to known about him already and he's getting plenty of attention'. Further details in the print edition.