Baltimore gave up right-handed prospect Denny Bautista for
Grimsley, who immediately agreed to a contract extension through
Grimsley, 36, is 3-3 with a 3.38 ERA in 32 appearances for the Royals this season.
Since signing with Kansas City before the 2001 season, Grimsley leads AL relievers with 251 appearances, with a 3.94 ERA over that span.
For his career, he's 38-50 with a 4.75 ERA in 13 seasons.
Bautista, 23, began the season at Double-A Bowie before making his major league debut on May 25. He made two relief appearances, allowing eight runs in two innings, before being optioned back to Bowie.
The Orioles' bullpen has struggled since right-hander Rodrigo Lopez was made a starter in May. Lopez was sent back to the bullpen
last week, but injuries may force manager Lee Mazzilli to return
him to the rotation.