Clips show cast members and musical performers enjoying the sunshine in scenes filmed over the summer on an outdoor set.
Sammy Winward - who plays Katie Sugden - said that the shoot "[felt] like a real festival".
"It's so exciting," she said. "There's huge tents, VIP areas, the stage, people walking round... It looks brilliant."
Emmerdale's series producer Stuart Blackburn had previously described the scenes as "technically... one of the biggest challenges" the show had ever faced.
"This festival represents the modern countryside - vibrant, young and energetic," he added. "It was an amazing feat to put together an entire festival in such a short space of time."
Scouting For Girls, who headlined the event alongside The Proclaimers, said that they were honoured to have been asked to perform.
"It feels amazing to be part of the 40th anniversary of Emmerdale," they said backstage at the event. "We're really excited."
Drummer Pete Ellard - who is a huge fan of the show - even admitted that he'd consider a change of career if offered a role in the soap.
"If they offered you a part today, would you leave the band?" asked lead singer Roy Stride.
"Yeah!" replied Ellard. "Wouldn't you?"
Emmerdale celebrates its 40th anniversary on October 16. A special live episode - as well as scenes featuring Homefields festival - will air the week beginning October 15.
Watch Scouting For Girls discuss filming at Homefields below: