The Cubs designated Cowles for assignment Sunday, Jared Wyllys of AllCHGO.com reports.
After being claimed off waivers by the Cubs in January, the 26-year-old will lose his place on the 40-man roster to clear space for the signing of Shelby Miller (elbow). Cowles will now be exposed to waivers, but he'll likely stick in big-league camp even if he goes unclaimed.