Bills general manager Brandon Beane said Monday on WGR-AM 550 in Buffalo that Allen will begin as the team's No. 3 quarterback, behind AJ McCarron and Nathan Peterman.
Those three will then compete for the starting job.
McCarron was signed as a free agent in March after being a backup with the Cincinnati Bengals. He is expected to be the Bills' No. 1 quarterback at the outset, but it remains to be seen whether he can fend off a challenge by Allen.
McCarron has played in 11 NFL games and has not started a game since 2015, when he started three games for the Bengals. Cincinnati had a 2-1 record in those starts.
Peterman started two games for the Bills last season, and the team went 1-1 in those starts. He completed 49 percent of his passes with two touchdowns and five interceptions in the four games he played last season.
The performances of those two quarterbacks would seem to give Allen a chance to work his way up the depth chart to become a starter sooner rather than later.
Carson Wentz of the Eagles, Derek Carr of the Raiders and Russell Wilson of the Seahawks all became starters as rookies despite having teammates ahead of them on the depth chart when they began practice.