The win was Cahill's second of the season without a loss, going 8 innings, fanning 9 and allowing one run, which came in the 6th inning, after the A's had already forged a 4-0 lead.
Cahill was strong, throwing 80 of 112 pitches for strikes as the A's moved back to .500, at 8-8, five games behind NL West leader, Texas.
The Cubs may have snapped Colorado's win streak on Saturday, but the Rockies went right back to starting another one with a 9-5 win at Coors Field on Sunday.
Doing his fair share to keep Colorado in first place in the NL West, Carlos Gonzalez went 4-for-5 (all singles), scored a run, stole a base and drove in two runs.
Gonzalez has 12 RBI on the season, and has hit only one home run thus far, but it's not a worry as the Rockies lead the Giants by 3 1/2 games in the division.