Scahill, the Rockies' eighth-round pick in 2009, will be making his Major League debut. He pitched all season in the Colorado Springs rotation, going 9-11 with a 5.68 ERA. He struck out 159 and walked 74 in 152 innings.
Manager Jim Tracy said he will try to get Scahill in a game quickly to get his feet wet. After that it will be determined whether Scahill will be used in a piggyback role or as a more traditional reliever.
"I think settling a young kid in is really important instead of just throwing him to the wolves," Tracy said. "I don't want to feel like we're doing that to him."
McBride made his Major League debut on Aug. 4, against the Giants. He played in nine games, hitting .200 with two RBIs, before being sent back to Triple-A.
Colorado Springs manager Stu Cole and hitting coach Rene Lachemann will also be moving up to the Majors for the final month of the season.