Reba McEntire Surprises Little Big Town with an Invitation to Join the Grand Ole Opry

Little Big Town's Kimberly Schlapman and Karen Fairchild with Reba McEntire

By Nancy Kruh

10/04/2014 AT 11:10 AM EDT

Little Big Town's Jimi Westbrook knew this wasn’t going to be just any other night on the Grand Ole Opry's stage when his in-ear monitors picked up a fifth voice joining the group on the last chorus of their hit "Pontoon."

"I thought, who's singing?" Westbrook recalled later backstage at the Opry House in Nashville Friday. His wife, bandmate Karen Fairchild, was equally mystified, wondering, “Who's singing an ad lib that we didn’t talk about?”

The answer soon came into view as Country Music Hall of Famer Reba McEntire walked on stage and presented the quartet with an even bigger surprise: an invitation to become the newest members of the Opry.

Too shocked to answer, Kimberly Schlapman buried her face in her hands, Fairchild slumped onto McEntire's shoulder, Phillip Sweet slapped his forehead, and Westbrook did a backbend worthy of an Olympic gymnast. All their eyes were filled with tears.

"Well," McEntire announced over the crowd's cheers, "I'm taking that as a yes."

After the performance, the four were still struggling to find words to describe how important the night was to their career. Their official induction will be on Oct. 17. "People ask, 'How do you know when you’ve made it?’' " Westbrook said. "Now I know."

"This is like the pinnacle," Fairchild said. "This is forever. Here, in the ladies' dressing room tonight, I was looking at [photos of] Emmylou [Harris] and Dolly [Parton] and Patsy [Cline], and now we’re going to be ... "

"In the club," Schlapman finished.

"I just freaked out right there," Sweet said, holding up an arm to show off the goose bumps.

Watch the big moment below: