Peacock was traded from the Diamondbacks to the Royals on Sunday in exchange for cash considerations.
Peacock allowed two runs in 2.2 innings in his first two major-league appearances of the season before being designated for assignment by Arizona on Thursday. The right-hander will now land a spot on the Royals' 40-man roster, and he'll likely report to Triple-A Omaha after Domingo Tapia was designated for assignment Sunday.