Socolovich, 24, was 4-0 with two saves and a 2.11 ERA in 31 relief appearances between Triple-A Norfolk and Triple-A Iowa. He struck out 57 hitters over 55 1/3 innings and walked 14.
He was a non-roster invitee to the Orioles' Spring Training camp, and had three stints with the big league team, appearing in six games. He was designated for assignment Aug. 14.
The Cubs already have used a franchise high 27 pitchers this season. It's the most since 25 hurlers were used in 1999.
The 27 pitchers used ranks third-most in the Major Leagues this year behind the Blue Jays (32 pitchers) and Padres (30).