The Lindsay star called her boss during a pre-taped appearance on The Late Show, airing Wednesday.
The actress, who calls Winfrey her "mentor," suggested that she should give the talk show icon a ring. "I think maybe I should just call her right now," the 27-year-old actress told host David Letterman, pulling out her cell phone. "Should we call Oprah?"
"No, we're not," said Letterman, who settled his longstanding feud with the TV titan in January 2013.
"I think so," Lohan told him. "Is there a phone? Have you got a phone?"
"We're not calling Oprah," Letterman said defiantly.
The 2 Broke Girls guest star encouraged the audience to chant "Op-rah! Op-rah! Op-rah!," prompting Letterman to finally call Winfrey using a phony voice. When the 60-year-old got on the line, Letterman asked, "Yes, could I speak to Oprah Winfrey, please?...Hi, this is Lindsay Lohan's secretary."
"Who is this?" Winfrey asked, and Letterman, using his regular voice, admitted, "It's Dave, Oprah."
"Oh my God," Winfrey laughed. "Very good, Dave! The David Letterman who's retiring?"
Letterman then asked Winfrey how she thinks Lohan is doing now. "I think she's doing okay. What do you think?" she asked.
"I've loved her since she was 6 years old," he said.
"I think she's doing really okay," Winfrey reiterated. "I think, you know, to have cameras following you around for every phase of your life, and you are trying to pull your life together, I think that's a really difficult thing, so, yeah, we're really pleased she's making some progress." Lohan then got choked up.
"Oprah, I've spent 30 years trying to pull my life together," Letterman joked. "Where the hell have you been?" Winfrey then replied, "Dave, you should be doing okay, because the last time I was there we discovered that we have the same meditation teacher, and now Lindsay's doing meditation, too."
Without missing a beat, Letterman fired back, "You know what else, Oprah, that I've switched to now, that is really fantastic?" After a beat, he told the talk show icon, "Scientology!" That promoted Winfrey, Lohan and the entire audience to laugh. The actress then said, "Oh goodness, gracious!"