The pair of prospects were added in advance of next month's Rule 5 Draft -- protecting them from being taken by another club -- and put the Orioles' 40-man roster at capacity. Major League Baseball's deadline to protect players is Tuesday at 11:59 p.m. ET.
"They are young, they are strong and they distinguished themselves in Double-A," Orioles executive vice president of baseball operations Dan Duquette said of Schoop and Belfiore.
"Belfiore has had a good year. He pitched well in the California League, he pitched well in the Arizona Fall League and also in the Eastern League. And he's very tough on left-handed hitters. Schoop can play the middle of the diamond and he can hit. He's got some power."
Schoop, 21, batted .245/.324/.386 in 124 games for Bowie in 2012. He was the Orioles' Minor League Player of the Year in '11 and was signed as a non-drafted free agent out of Curacao on Aug. 20, 2008. Following the '12 season, Schoop batted .270/.446/.429 with two home runs and 10 RBIs in 21 games in the Arizona Fall League and was selected to play in the Rising Stars Game, the league's All-Star Game.
Belfiore was also named to the Rising Stars Game this fall, and posted a 2.61 ERA with 11 strikeouts and three walks in his final 10 1/3 innings for the Mesa Solar Sox. He is currently ranked by MLB.com as the organization's No. 14 prospect -- with Schoop listed at No. 3 -- and Belfiore credits a return to relief in June 2011 and cleaning up his mechanics for his successful '12.
"It's probably been my best year because I got back to my comfort zone," Belfiore said of the first full season he's had as a pro exclusively out of the bullpen. "In college, I was a closer full-time, never started. It was definitely an advantage going back to what I was comfortable with. I learned a lot from this year.
"The D-backs kind of strayed away with what I was doing [as a starter], and I was able to get back to that in the bullpen. And then getting traded obviously opened the door for me as well."
Belfiore came to the Orioles to complete the trade of infielder Josh Bell, leaving the organization that drafted him in the first round (45th overall) out of Boston College in 2009. Belfiore, who had a 2.37 ERA with 28 strikeouts and five walks in 19 innings with Arizona's high Class A Visalia, posted a 2.85 ERA in 28 games with Bowie.
Players signed at age 18 must be protected within five years or they become eligible to be drafted by other organizations through the Rule 5 process. Players signed at 19 or older are to be protected within four years. Clubs pay $50,000 to select a player in the Rule 5 Draft, to be held on Dec. 6 at the conclusion of the Winter Meetings in Nashville, Tenn. A player must stay on the 25-man roster for the full season or be offered back to his former team for $25,000.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.