Blake Beavan will move into the bullpen in a long relief role, with Harang taking his spot.
"He's a veteran guy and he knows what he needs to do to go out and be successful," Wedge said. "He has a great feel for himself, he's had a tremendous amount of success at the big league level. He had 31 starts last season and had a pretty good year [with the Dodgers]."
Wedge said moving Beavan to the bullpen provides a needed long man for a relief crew now minus Kameron Loe, who was designated for assignment on Thursday to make room for Harang.
"Hopefully it's a win-win for us," Wedge said.
Beavan won 11 games last year for the Mariners, but has struggled in two starts this season with an 8.44 ERA and opponents batting .348 against him.
"He's still a young pitcher figuring it out," said Wedge. "He needs to continue to improve. Sometimes when you move somebody to the bullpen it's a different look and feel. Maybe that helps him along the way, too."
Rookie Brandon Maurer, who lasted just two-thirds of an inning in his last start and is lugging an early 16.20 ERA, will remain in the rotation for now.
"I like his arsenal of pitches and his stuff," Wedge said. "He's a young guy just getting his feet wet and I believe you've got to give him a little bit of time. Blake is a little further along experience-wise, but you have to like the stuff of Maurer. And each time he goes out there, you'll see him continue to figure things out and improve. You've got to stick with guys."
Harang, an 11-year veteran with a career record of 105-104 and a 4.19 ERA, said he was just happy to finally know where he'll be playing after getting dealt from the Dodgers to the Rockies and now Seattle in the past week.
"It's just nice to get back out and be doing it on a big league field," Harang said after his bullpen session. "I was throwing this last week at San Diego State when I was home, just trying to stay sharp and ready to go. I threw five innings against live hitters one day and a bullpen on Sunday, just making sure to keep my arm strength up and stay as sharp as possible."