The actress opened up about the end of her career during an interview with the New York Times ... admitting her new role on "Matlock" -- where she plays an older, gender-flipped version of the same character from the '80s drama -- is her last part.

The way Bates tells it ... she was considering moving on from acting -- telling her agent she was offically done after a poor experience on a movie set. She wouldn't say which one.

Then, she says the script for "Matlock" came in ... and, she instantly fell in love with the character right wrongs -- since she faced so many earlier in her life and career.

That said, KB's clear ... this is the last dance -- with no designs to jump on another great drama, even if an excellent script crosses her desk.

Bates say it's exhausting playing the character ... the 18-episode order certainly taking a toll on the star as well.

Bates has had a prolific career, appearing in some of the biggest movies of all time like "Titanic," "The Blind Side" and recently appearing in "The Family Affair" alongside Zac Efron and Nicole Kidman ... with her Oscar winning role in Stephen King's "Misery" proving a high watermark in her career.