The 60-year-old Oscar-nominated actress will take on the role of Marie Carter who was known to beat her grandson while raising him at her brothel in Peoria, Illinois.
The comedian's widow Jennifer Pryor said Winfrey was eager for the role after getting hold of the script, according to an article on Tuesday by TMZ.
New role: Oprah Winfrey, shown in March in Los
Angeles, will portray the brothel-running grandmother of the late
comedian Richard Pryor in an upcoming biopic
Winfrey shared an Instagram snap on Sunday showing herself with director Lee Daniels and actor Mike Epps, 43, who will portray the late comedian.
'@theoriginalbigdaddy , @eppsie , and me just finished a great 1st read session. #RichardPryorMovie,' Oprah wrote in the caption for her more than three million followers on Instagram.
Daniels also posted a similar Instagram image on Sunday with the caption: 'And we're off... Get ready y'all for #richardpryor'
Comedy legend: Richard Pryor, shown in November 1977 in New York City, will be portrayed by Mike Epps in the biopic
Winfrey previously worked with Daniels, 54, on his 2013 film The Butler.
Epps beat out Nick Cannon, Marlon Wayans and Michael B. Jordan to play Pryor in the highly anticipated biopic.
There has been no word yet on who will portray the comedian's widow Jennifer, who is also producing the film.
Casting rumours have mentioned Kate Hudson and Anne Hathaway as frontrunners for the role, according to an article by Entertainment Tonight.
Getting started: Opra and Lee Daniels shared an
Instagram snap on Sunday of themselves with Mike Epps after a reading
session for the movie
Pryor's mother Gertrude was a prostitute in his grandmother's brothel and she abandoned Pryor when he was age 10.
He was raised primarily by his grandmother Marie Carter who was known for being a violent woman who would beat him as a child.
Pryor was a comedy legend known for his profanity-laced stand-up routines, his Grammy-winning comedy albums and also for his 1970s movies including Silver Streak and Car Wash.
Longtime couple: Jennifer Lee and Pryor, shown in 1994 in Los Angeles, remarried in 2001
The Blazing Saddles co-writer infamously set himself on fire in 1980 while freebasing cocaine.
Pryor suffered a heart attack and died on December 10, 2005.
His widow Jennifer has all rights to her late husband's material and recordings and has been working with Daniels on the biopic.
Funny guy: Pryor, shown in 1988 in New York City, is considered one of the most influential stand-up comedians of all-time
