EXCLUSIVE: Oprah Winfrey on Her Return to Acting in 'Greenleaf': 'It's So Good!'

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Oprah Winfrey spoke to ET about returning to acting as she went to work starring in her first TV series in decades, Greenleaf.

"Oh my gosh! It's so good!" Winfrey gushed to ET of the show.

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Winfrey liked the pilot -- which was created by former Lost and Six Feet Under writer Craig Wright -- so much, she is executive-producing the series and made it her first recurring TV role since 1990's Brewster Place in 1990.

The upcoming series centers on disillusioned preacher Grace Greenleaf (Merle Dandridge), who has returned home to her estranged family after 20 years. As she re-enters the world of Calvary Fellowship World Ministries, the Memphis megachurch run by her powerful parents: Bishop James Greenleaf (Keith David) and Lady Mae Greenleaf (Lynn Whitfield), it becomes evident that things are not as virtuous as they seem and that the family's outward display of faith hides sin and misdeeds.

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For fans concerned about how the series might portray religion, Winfrey, who grew up in church, put all worries to rest.

"I am never going to be disrespectful to the church. I can tell you that," Winfrey said. "I'm never going to be disrespectful, because it is the rock and foundation of who I am, so I would never do anything that disrespected that. Now, would I use it as a basis for telling stories about people who are flawed? Yeah, but I'm not going to do anything to disrespect it."

Winfrey plays Grace's aunt Mavis, a boozy potty-mouthed blues club owner, which is a character that plays totally against type for her.

"I didn't know diddly-do about blues!" Winfrey admitted with a laugh.

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While she might not know much about blues, Winfrey knows everything about producing for television. As executive producer of the series, Winfrey also gets to call the shots.

"I love the casting process!" Winfrey said. "I love getting the little clips of people in their auditions. I like being involved."

Greenleaf debuts June 21 on OWN.