McClain was congratulated by several teammates and Iowa coaches after learning of the promotion and was scheduled to board a red-eye flight to Chicago early Saturday morning.
He was expected to be activated in time for Saturday's 12:20 p.m. CDT game against the Florida Marlins at Wrigley Field, which will be televised on FOX.
"Offensively, you have to go with him as this team's MVP," said Iowa hitting coach Pat Listach, the 1992 American League Rookie of the Year with the Seattle Mariners, now in his fifth season with the I-Cubs. "These older players, we need every piece of their puzzle to fit together for the good of this team."
McClain said with a modest chuckle, "It's been a while since I was up there (in the show). It's exciting. I felt like I was putting together a pretty decent season here. Of course you see the injuries that take place, but I was just trying to finish up strong."
McClain started Friday's game at third base, but moved to first as part of a series of defensive switches in the seventh inning. He has been manning the right side of the infield often in the second half.
"It's been great playing first," McClain said. "It got me a lot more familiar on that side of the field, so that was nice. I've always played third, so I'm always comfortable there."
McClain had a noteworthy tryout with the Cubs in Spring Training 2004. He was one of the final cuts on Dusty Baker's roster and decided to return to Japan's Pacific League, where he appeared in 35 games with the Seibu Lions. He batted .184 and the following spring returned for another tryout with the Cubs.
In eight games, McClain was 5-for-17 with two doubles and three RBIs in Spring Training 2005. He hit .348 with a club-best six home runs in 24 games during Spring Training of '04.
Quade also praised McClain for his contributions with the Triple-A club this season.
"An MVP, for me, is someone who has been here all year," said the third-year manager of the I-Cubs. "McClain and Jermaine Van Buren have done it for us all year. If I could have two different categories, Scotty would win the offensive award and Jermaine would win the pitching award."
McClain added, "You never know what can happen. It's definitely been a long season, but I'm looking forward to it. I keep hearing about everything that goes on at Wrigley Field. I've never been there, so I'm pretty excited about the whole atmosphere and to play for the Chicago Cubs."
Barring Spring Training, McClain's last official taste of major league action was with the Devil Rays in 1998.