Johnson is 0-1 with a 13.50 ERA in one appearance with the Orioles this season.
The move is retroactive to May 24. Strop has struggled this year going 0-2 with a 6.11 ERA over 22 games. He has walked 14 batters and 17 2/3 innings.
Strop pitched in 70 games last year for Baltimore when he went 5-2 with a 2.44 ERA and played a large role in the Orioles success for 2012.