Oprah Winfrey RIPPED By Former Co-Star -- 'She Would Have Been a Field N**ger'

11:00 AM PT -- Rae Dawn Chong just released a video response on YouTube, saying she meant the n-word as a compliment.

Oprah Winfrey's former "Color Purple" co-star Rae Dawn Chong just UNLOADED on the talk show queen -- claiming O is a self-centered fat "biotch" who would have been a "field n**ger" back in the slave days.

Rae Dawn -- who's part black -- appeared on "Matty P's Radio Happy Hour" and talked about how her personal relationship with O went from good to really REALLY bad back in the 80s.

RDC says Oprah was "lovely" to her back on the set of Purple in 1985 ... but when Rae moved on to her next movie, "Commando," that's when she says O became "a total biotch."

"I starred in Commando. And she just wasn’t having me. She’s competitive. She didn’t like me. She just wasn’t having me."

It's clear, Rae doesn't like O either -- 'cause for the next several minutes of the interview, she ranted on and on about how much she hates Winfrey -- and stooped so low, she even took shots at her appearance and invoked slave imagery.

"If you look at the way [Oprah] looks, she looks like 60 years ago she would have been a house keeper luckily. She would have not been a house n**ger she would have been a field n**ger."

RDC continued the attack for several minutes. Among the lowlights:

-- "She's so enormously insecure. If you wanna distill Oprah Winfrey down to like her most basic components. She wants to be beautiful."

-- "Imagine being [Oprah]. She has all of the world. All the power in the world ... and she only wants something that is only chemical, purely impossible."

-- "The thing that’s really great about Oprah that you can't take away from her is that she's a great brown-noser."