Bosser is one of many ballplayers who only appeared in the major leagues during World War II. He made his major league debut in relief on April 29, 1945 in a doubleheader against the St. Louis Cardinals at Crosley Field. Fifteen days later he made his first big league start and was the winning pitcher in a 5-4 game against the Philadelphia Phillies at Shibe Park. His next win came in relief on May 30, also against the Phillies. His last appearance was on June 9, and then he was released by the Reds the next day.
In a total of 7 games he was 2-0 with 2 games started, 0 complete games, and 3 games finished. In 16 innings pitched he gave up 9 hits and walked 17. However, he allowed only 6 earned runs, so his final ERA was 3.38.
Bosser died at the age of 72 in Crossville, Tennessee.