Julia Roberts hit a professional milestone in 1989 with the release of “Steel Magnolias” ― but according to one of her co-stars, she was enduring some behind-the-scenes bullying from the movie’s director, Herbert Ross.

In a new interview with New York magazine’s Vulture, Sally Field described Ross being “very, very, very hard” on Roberts while filming the dramedy, which raked in more than $83 million at the U.S. box office ― a rarity for a female-led film at the time.

“If you ever talk to Julia, she’ll tell you,” Field said. “We would all rally around Julia, because she was the baby. She was sort of the newcomer. And she was wonderful, and he just picked on her. It was awful.”

As to why Ross might have singled Roberts out, Field said: “Because he could be a real son of a bitch, that’s why. Some people just need to have somebody they pick on. But we all came to her aid.”

Field, a two-time Oscar winner, said Ross didn’t subject her to the same treatment “because he dared not.”

“I mean, I don’t mind notes, but I will argue if it doesn’t make sense to me,” she explained. “But if you’re gonna be mean to me, then you’re gonna find a warrior. I may be small, but you don’t want to do that.”

Ross, whose Hollywood résumé also included “The Goodbye Girl” and “Footloose,” died in 2001 at age 74.

Based on Robert Harling’s 1987 stage play, “Steel Magnolias” follows a close-knit group of female friends in small-town Louisiana as they come to terms with the unexpected death of one of their own. Harling found inspiration for the story in his sister, Susan Harling Robinson, who died of complications related to Type 1 diabetes in 1985.

When translating “Steel Magnolias” from stage to screen, Ross and his team assembled an all-star cast that included Olympia Dukakis, Daryl Hannah, Shirley MacLaine and Dolly Parton in addition to Field and Roberts.

Before Roberts landed the part of Shelby, the ill-fated daughter of Field’s character M’Lynn, actors Meg Ryan and Winona Ryder were among those famously considered for the role.

At the time of her casting, Roberts had only a handful of film credits, most notably the 1988 romantic comedy “Mystic Pizza.” Among those who had no doubts about Roberts’ talent and charisma, however, was MacLaine, who told People in 2019 that she knew instantly the future “Pretty Woman” actor was destined to be a star.

“We were rehearsing on a sound stage, I can’t remember where, and she walks in,” MacLaine said. “And the way she walked into the room and sat down and said hello... I got up from the table and called my agent before we even started to rehearse. I said, ‘There’s a woman here and she’s going to be a huge star. You should handle her,’ I told him. She was amazing. The energy that she had just walking into the sound stage.”