Avery, who played with the O's from May 13 to May 29 and hit .217, said his return to the 25-man roster was "a big surprise."
"You never know what to expect," Avery said. "I'm very happy to be back and playing up here."
To make room for Avery, Nick Johnson has been moved to the 15-day disabled list. Johnson started at designated hitter on Thursday and left the game after fouling off a changeup during his only at-bat, causing pain and weakness in his right wrist, which has been plagued by injuries throughout his career.
Johnson said he can only make one swing before sharp pain and a loss of strength make it difficult to continue.
"I got one bullet to use per at-bat," Johnson said. "The strength comes back, but it takes too long. We'll see if I can't calm it down.
"I am fine if I hit the ball. If I foul it off, it's pretty painful."
Johnson is scheduled to undergo an MRI on Friday morning and will be eligible to return the first day after the All-Star break.
Johnson and manager Buck Showalter were optimistic that the wrist injury would be substantially less serious than his previous problems.
The O's tested Johnson's wrist extensively during Spring Training, and Showalter said head athletic trainer Richie Bancells had been frequently using massage to try to keep the scar tissue under control.
"I feel a little bit for Nick," Showalter said. "I'm hoping it's something to do with some of the healing with those surgeries, as opposed to something giving way in there."
"It didn't really swell up like it has in the past," Johnson said. "Maybe a couple cortisone shots will do the trick. I don't know. Hopefully, nothing is wrong with it and maybe that can take some of the pain away, like it has in the past. We'll see what the doc says."
Avery played 15 games with the Orioles in May, going 10-for-32 during the first eight before a 3-for-28 slide in the final seven.
"It was an experience for me," Avery said of his time in the Majors. "The experience is what teaches how to get better and how to make adjustments, so it was definitely a benefit."
Avery was sent back down to Triple-A when Endy Chavez came off of the disabled list on May 29, as Showalter thought normal playing time would give Avery an opportunity to work out a few kinks in the Minors.
Avery noticed that he was seeing more offspeed pitches in hitter's counts in both the Majors and Minors, but he said he has made the necessary adjustment.
In his last 11 games with the Tides, Avery hit .333 with six RBIs, eight walks and five steals.
Avery becomes the second true outfielder on the O's active roster, joining Adam Jones.
With Nolan Reimold and Nick Markakis on the disabled list, starting corner outfield spots are there for the taking, a big part of the reason Avery was in the Baltimore area even before the team knew Johnson's injury would create an opening.
"I'm just focusing on doing my job," Avery said. "That's helping the team, so if I can do that, I'm happy."
"I'm going to try to play him as much as he allows me to, if that makes any sense," Showalter said. "Xavier brings some things that you can't teach. He's a somewhat raw player that is starting to figure out some of the intangibles and some other things. I'm patient, but at the same time, I think Xavier comes here with his eyes open now about what he's being asked to do. There shouldn't be any wide eyes, he's played in this ballpark before against Major League competition. So hopefully that bodes well for us."
Greg Luca is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.