Miller signed another one-year extension with Rangers in November 2015. On 2 January 2016, Miller became Rangers' oldest ever player to score a hat-trick in a 6–0 win over Dumbarton. Five goals in four league games during January 2016 saw Miller win the Scottish Championship player of the month award. He played and scored in the 2016 Scottish Challenge Cup Final, as Rangers beat Peterhead 4–0, only five days after Rangers had secured the Scottish Championship trophy. Miller ended the 2015–16 season with 21 goals, scoring his final goal in the 2016 Scottish Cup Final which Rangers lost 3–2 to Hibernian, giving Hibernian their first Scottish Cup win since the 1901–02 Scottish Cup.