The entertainer repeatedly put his hands inside the freelancer's baggy denim shorts as far as her hips while making a programme in Australia in the mid-1980s, she told his indecent assault trial.
On one occasion while groping her that day, Harris even discussed her legs with the programme's male director, who was standing next to them, she told the jury.
The woman, who gave evidence from behind a screen and cannot be named, told Southwark Crown Court, London, she later found out Harris's nickname was "the octopus".
She told the jury she later complained to her female supervisor: "That dirty old man groped me all day."
Harris, 84, denies 12 counts of indecent assault between 1968 and 1986.
The woman, who was in her 20s at the time, said he first touched her while sitting in the make-up chair in the morning. She said he then did it repeatedly as she reapplied make-up to his face during the eight-hour studio shoot.
When Sonia Woodley, QC for Harris, suggested the events had never happened, the woman gave a dismissive snort.
The trial continues.