Scahill is available to pitch out of the bullpen in Sunday's game against the Milwaukee Brewers.
The Rockies also returned righty Wilton Lopez to the Sky Sox.
This is the first call-up this season for Scahill, who was 1-1 with a 3.93 ERA in 24 appearances with the Sky Sox. In 29 major league games, all with Colorado, Scahill is 1-0 with a 4.29 ERA.
Lopez had an 11.37 ERA in four games with the Rockies this season before he was designated for assignment June 9. He is 0-2 with a 4.54 ERA in 20 games with the Sky Sox.
The Rockies have 39 players on their 40-man roster.