The Orioles traded Cook to the Pirates on Tuesday in exchange for Patrick Reilly.
Cook has impressed since earning a promotion to Triple-A in April, slashing .282/.373/.490 with 43 RBI and 12 stolen bases in 69 games. The 25-year-old has also played every position in the field other than shortstop this season, which may increase his chances of earning a call to the majors later in the year.