Kolarek, a 26-year-old left-hander who was selected in the 11th round of the 2010 draft by the New York Mets, was released by that organization a few weeks ago. He was 2-4 with a 4.43 ERA in 51 games (one start) for Double-A Binghamton.
Joseph, who turns 27 Wednesday, hit .280 with six homers in 63 games while playing primarily second base with Double-A Bowie. He is the younger brother of Orioles catcher Caleb Joseph.
In other news, The Sporting News announced Monday that Texas' Prince Fielder had won its 2015 American League Comeback Player of the Year Award, which is voted on by a panel of players.
Orioles third baseman Manny Machado, who returned from knee injuries that ended his season the past two years, finished fourth in the voting. New York's Alex Rodriguez and Cleveland's Jason Kipnis were second and third, respectively.