Williams, 28, is said to be a bit ahead of the schedule set by team doctors. He had surgery in November to remove bone spurs that were tearing at his Achilles' tendon.
"Yeah, it's good to be back even for just a few plays here and there," Williams said after taking part in about half of the full-team sessions at Bills OTAs. "Just getting my foot in the door. And hopefully, when we get to training camp, I can be full bore."
Williams has been a starter and consistent performer for the Bills since being selected in the fifth round of the 2006 draft. He made the Pro Bowl in both 2009 and 2010 before the foot injury cost him all but five games last season.
If Williams is healthy, the Bills could have football's best defensive line. The team opened up their wallet in free agency to lure pass rushers Mario Williams and Mark Anderson. Add to the mix defensive tackle Marcell Dareus -- last year's No. 3 overall pick -- and Buffalo has a front line with the potential to be dominant.