The Bills activated Spiller on Friday, after he missed the last eight weeks due to a broken collarbone. He suffered the injury against Minnesota in Week 7.
Buffalo had until 4 p.m. ET Saturday to activate Spiller.
Spiller's return should be a boost for Buffalo's struggling running game. The Bills rank 24th in the league in rushing with an average of 97.5 yards per game.
The Bills (8-6) opened a roster spot for Spiller on Tuesday when they released fullback Frank Summers. Spiller is officially listed as probable for Sunday's game against Oakland (2-12).
Information from The Associated Press was used in this report.