Cornish, who had four touchdowns to help the Stamps go 4-1 in October, was named offensive player of the month and top Canadian.
The special-teams honour went to teammate Rene Paredes and Montreal Alouettes linebacker Chip Cox was named defensive player of the month.
Cornish, a native of New Westminster, B.C., had 606 rushing yards on 75 attempts last month and added eight receptions for 83 yards. He finished the regular season as the CFL's leading rusher with 1,813 yards and had the most touchdowns with 14.
Paredes was 16 for 17 on field-goal attempts last month. Cox, meanwhile, had 24 tackles, six sacks, two special teams tackles and an interception over five games.