Avery hasn't slept since arriving in Baltimore around midnight, having his contract purchased just prior to Sunday's game and then batting leadoff and starting in left field in the series finale against the Rays.
Avery joins Steve Tolleson and Bill Hall as Orioles players who have started this week in their first game after getting the call up from Triple-A.
To make room for Avery, the Orioles optioned reliever Stu Pomeranz to Triple-A Norfolk and designated infielder Matt Antonelli for assignment.
Pomeranz was brought up on on Monday as a result of Baltimore's 17-inning game with Boston on Sunday and threw four scoreless innings during his first week.
Antonelli hit .204 with one home run and seven RBIs in 29 games with Norfolk after being signed on Nov. 21, 2011.
"Thinking of the idea of coming up here and playing, man, I don't even know how to explain it to you," Avery said. "I'm still in awe right now. I can barely talk to you right now. I'm so happy to be here because there's no place like the big leagues. This is the show."
Avery's express trip to the big leagues started picking up steam in Spring Training, when he hit .283 in 13 games.
That hot start translated to Norfolk, where Avery hit .273 and stole eight bases in 33 games.
"Xavier has done a good job taking some of the things that he was exposed to in Minor League camp and taking them to Norfolk," manager Buck Showalter said. "We just hope to keep it going, he's doing well down there."
Avery had been especially hot of late, hitting .429 with three home runs and nine RBIs in his last nine games.
"It's just my approach," Avery said. "I'm getting myself in hitter's counts and I'm taking full advantage of the situation when I get in those counts."
Avery expects to be comfortable in left field, where he made six of his 33 starts with Norfolk this year. Avery said he's played left field going back to high school and doesn't expect it to be a challenge for him.
Avery said he was focusing on staying calm and focused, and Showalter has tried to avoid discussing nerves and anxiety with him.
"I don't know, that's why it's fun to watch," Showalter said. "I'm looking forward to seeing [him] today."