Keeffe was the most experienced of the quartet, playing 40 games for the Pies before serving a one-year drug suspension in 2016. He returned to the club in 2017 with the Magpies re-drafting him in the rookie draft. However, he failed to play a senior game in 2017.
Schade joined Collingwood at the end of last season after 20 games in five seasons at the Gold Coast Suns, but managed to add just eight matches to his tally at the Magpies.
Both Mackie and McCarthy failed to make their senior debuts for Collingwood.
“We first met Lachy when he was a 17-year-old soccer player in Gympie, and over the past ten years he’s become a very popular and impressive young man at the Collingwood Football Club,” Collingwood football manager Geoff Walsh said.
“Henry, Liam and Mitch made the most of their opportunity coming through the Rookie Draft and committed to the football program and their teammates over the past 12 months at the club.
“We thank all four players for their contribution to both the AFL and VFL teams and wish them all the best for their future endeavours.”