Crazy Horses trio Jay, Merrill and Jimmy Osmond popped into the Coseley branch of the fast food restaurant following their performance in Boogie Nights at Wolverhampton's Civic Hall.
All three posed for photographs and signed autographs for amazed staff after their gig on Thursday night – but not before selecting their favourite tasty treats from the menu.
The brothers ordered a Big Tasty Meal with bacon, a Big Mac Meal, Quarter Pounder Meal and six chicken nuggets as well as an orange juice, two bottles of water and a blackcurrant and apple flavoured Fruit Shoot.
Shift manager Josh Paul, who had his photograph taken with the trio, said: "I was in the office and one of that staff members came in and said there was someone famous in.
"I thought it was a tribute act or something at first, I mean this is Coseley McDonald's.
"They were really nice and stopped for about 20 minutes to have their pictures taken. They were really nice.
"When we were asking for autographs they were great about it. There was nothing big-time about them."
Mr Paul, 27, from Bilston, said the Osmonds were the most famous people he had had in his restaurant, although former heavyweight boxer Lennox Lewis called into the Bilston branch he was working in seven years ago.
He added: "One of the girls who wasn't working at the time was gutted because she is a big fan.
"She paid a lot of money to see them and if she had been working, she could have met them face-to-face.
"She only lives around the corner and was angry that I didn't call her up to come to the store."
The Osmonds have a liking for Wolverhampton. Last April staff and customers at Wolverhampton city centre menwear shop Blooms were surprised when Jimmy strolled through the door on a shopping trip.