He was 2-5 with a 3.56 ERA as a starter for Tacoma and 1-1 with a 2.38 in relief.
"I like both roles," he said. "I have grown to be more comfortable with [relief] than I was originally. But wherever they need me, I am happy to serve them there."
"The reports have been good," manager Don Wakamatsu said. "As a manager, you reflect back to last year and what he did against Minnesota, who we happen to be playing.
"He had a lot of success against [Joe] Mauer and [Justin] Morneau and that gives us some versatility. You want guys who can go multiple innings and with a lefty who has the ability to go situational, he gives us that."
Olson, who pitched a scoreless ninth Tuesday night vs. the Twins, and right-hander Sean White were recalled from Triple-A Tacoma before the game.
White, an important part of the Mariners' bullpen last season, was sent to Tacoma on May 19 to work on keeping the ball down in the strike zone.
He appeared to get himself straightened out, allowing runs in just two of his 15 relief appearances.
"It was tough at first going down, I am not going to lie about that," he said. "I felt I could use the time to my advantage and I feel I have done that.
"There was some stuff I wanted to work on, and I really feel it gave me a chance to do some of those things, including getting some consistency with my delivery. The biggest thing for me as a sinkerball pitcher is to keep the ball down so I get the results that I want."
White will team with right-hander Brandon League during the troublesome seventh and eighth innings.