He later scored on Jonathan Lucroy's sacrifice fly and Milwaukee hung on to even its record at 2-2.
Ex-Cub Aramis Ramirez contributed two RBI for the Brewers.
Shaun Marcum (1-0) earned the victory after holding Chicago to three runs on five hits over six innings, walking none and fanning six.
John Axford picked up his first save by getting the final two outs in the ninth.
Darwin Barney and Bryan LaHair each socked solo homers for the Cubs, who lost for the third time in four games.