Harriet Oleson was portrayed by Katherine MacGregor, however she was credited as Scottie MacGregor for the majority of her roles prior to Little House on the Prairie. She did not appear on the final episode of the show as she was in India at the time.
While she had appeared in many shows prior to her role as Harriet Oleson, it was her last mainstream role after the show ended its run. She did appear on Broadway and off Broadway as well.
Katherine MacGregor lives until 2018, when she passed away in California at the age of 92.