The Expos called Barrett up to the MLB on September 19, 1998, in a game against the Philadelphia Phillies as a third baseman. He managed to hit a home run and a single in the game. After only playing eight games as an Expo, Barrett was sent to play for the Harrisburg Senators, a Class AA team from the Eastern League. He recorded 145 hits, and seventy-eight runs, nineteen home runs, and eighty-seven RBI en route to winning the Double-A All-Star Catcher and Montreal Expos Minor League Player of the Year awards. His performance allowed him to claim a spot on the Expos’ starting roster during the 1999 season. During his first full season, Barrett had fifty-nine starts as a catcher, sixty-two as a third-baseman, and six as shortstop. He also led all National League rookies with thirty-two doubles, while ranking as one of top statistical tiers in runs, hits, and run batted in among all other rookies.