The workout was earlier reported by the Buffalo News.
Young presents a dual threat as a runner and passer, and would be regarded as a good fit in coach Chan Gailey's Wildcat formations.
Young spent last season with the Philadelphia Eagles. He struggled in six games and threw for 866 yards, four touchdowns and nine interceptions. Young also had a career-low 60.8 passer rating in 2011.
The Bills were expected to draft a developmental quarterback last week to learn under Fitzpatrick but passed. Buffalo has Fitzpatrick as the starter and Tyler Thigpen as the backup.
Young has had an up-and-down career since being selected third overall by the Tennessee Titans in the 2006 NFL draft. He was the NFL's 2006 offensive rookie of the year, but eventually lost his starting job on several occasions in Tennessee before the Titans ran out of patience with him.
In assessing the Bills' draft on Saturday, general manager Buddy Nix noted the team had missed out on selecting a quarterback prospect it was interested in, before adding Buffalo would pursue other options.
"We're going to get one in free agency," Nix said. "We're going to bring in a quarterback, and we think a good one."
Young's athletic ability is not in question. He's still regarded as a solid dual threat with his strong arm and ability to take off and run. What remains unknown is how the highs and lows Young has endured during his six-year NFL career have affected him, and how suited he might be to fill a complementary role.
In April, Young told The Tennessean that he would prefer being a starter but was keeping his options open.
"Sure, I'd like to (start). Everybody feels that way," Young told the newspaper while participating at a charity basketball game. "But all I can do is come in and compete. It is like I am getting drafted all over again. You go in and compete and let the coaches and front office people make that decision."
Information from The Associated Press was used in this report.