After graduating from Manual Arts High School, Lefebvre had a long career in professional football that spanned from 1934 to 1949.

In a 28–0 win against the Western Eagles, he scored a safety by tackling Paul Neva as the latter attempted to run on a fake punt.

[7] Standing five feet, six inches, and weighing just 150 pounds, he was the smallest player on the team and was dubbed their "mighty mite.

"[8][7] On October 20, Benny started at halfback for the Maroons, and faced off against his brother Gil, who was the starter in the same position for the Hollywood Braves.

[10] A ten-yard run by Lefebvre to the Braves' one-yard line set up the game-winning score by Jim Keefer.

[11] The News-Pilot reported that he "played a starring role" in the game which "was replete with spectacular passing maneuvers" and was "a thrilling pro football" match.

[11] Newspapers reported that he "weighs but 150 pounds but has proved to be one of the hardest men to stop in the uptown pro games.

"[12] The Los Angeles Times reported that Lefebvre "is one of the shiftiest open-field runners in the professional league and is the player most feared by Coach Dick Mulhaupt's [Westwood] Cubs.

[15] The Maroons lost 14–21 after blowing an early lead, allowing the Braves to score 15 points in the final quarter.

[16] Lefebvre helped the team eventually reach the league championship, where they lost 6–10 against the Westwood Cubs in an upset.

[19] Late in the season, he and his brother were part of Erny Pinckert's All-Stars, who lost 20–51 in an exhibition game against the Chicago Bears.

[4] In 1946, Lefebvre served as coach of the Spoilers Athletic Club, as well as the football team at Southern California Military Academy.

In 1971, The Los Angeles Times reported that he "is reputed to have more alumni playing major league baseball than any other sports camp director.