The couple, who are engaged and have six children together, have asked Oliver as well as his wife Jools and Clooney and current girlfriend Stacy Keibler to join them for the bash at their Surrey home, reported Sun online.
"Brad and Ange hold a Midsummer Night party every year and always base the theme around a specific country because it's a great learning opportunity for the kids.
"They've done Australia, Russia and Germany in the past but as they're living in London they've really got into the spirit of things with the Jubilee and the Queen's birthday.
"It'll be like a British fete, with all the traditional games and cream teas in the garden in the afternoon," a source said.
The duo is also said to be hosting their own Olympic opening ceremony party.
