Two goals from Jean-Claude Darcheville and another from Kris Boyd lifted Rangers past St. Mirren, but Celtic maintained its edge on goal difference at plus-four.
Beasley, who was hurt playing in a European Champions League match against Stuttgart, came on in the 77th minute for Nacho Novo.
Two days earlier, Rangers appeared to blow its league title chances when it was tied by Motherwell, 1-1.
It has already won the Scottish League and finished second to Zenit St. Leningrad in the UEFA Cup. It's favored to win the Scottish FA Cup Saturday when it meets Queen of the South.