Put on display in the straw nest, which covers an area of some 300 square metres, are Easter eggs and straw sculptures.
One of the organisers of the event, Domagoj Suster, said the organisers had planned to register the nest with Guinness World Records, but gave up on the plan because the registration procedure was too expensive.
He called on Osijek residents to bring their Easter eggs and put them on display in the nest, announcing various entertainment events.
Around the Easter nest are stalls put up by local associations, tradespeople and family farms presenting their products.
The "Easter in Osijek" programme will last until Tuesday.