The linebacker missed the first six games of the season after being handed a suspension for breaching the league's substance abuse policy.
The head coach told the team's website: "He had an outstanding practice. Obviously, he's got fresh legs and ready to roll and excited about the opportunity this week."
Miller added: "Oh, it was great. I was excited to be out there with all my teammates and my coaches, the linebacker corps. It was great. It was fun.
"That was the thing I was looking forward to the most, not the game so much, but just getting out there with guys, running around, building that esprit de corps. I think that I had a very good day today."
The Broncos next face the Indianapolis Colts.