Depending on where you live in Sydney, your local chicken shop might serve tabbouleh and chips, Portuguese tomato rice or green goddess salad. That’s because Sydney isn’t just divided by postcodes – it’s also divided by poultry.

In 2016, Twitter user Big Jez proposed an interesting theory – if you plot Red Rooster locations across Sydney, a near-perfect boundary emerges separating the city’s north-east from the south-west.

Big Jez called it the “Red Rooster Line”, but it’s also known in social policy circles as the Latte Line, the Colorbond Fence and the Quinoa Curtain. Running diagonally from Windsor to Carlton (later revised to include the airport store in Mascot), it carves the city in two, tracing inequalities – not just in Buffalo Crunch packs – but also in education, employment, property prices and even HSC results.

The idea gained traction a year later when Honi Soit editors Natassia Chrysanthos and Ann Ding expanded on it in the University of Sydney’s student newspaper. They argued it wasn’t just Red Rooster defining Sydney’s geography – other chains were also shaping the city’s boundaries, reflecting divisions of class and culture.

The theory also sparked interest in Reddit threads online and eventually flowed into mainstream news and academic papers.

Like Red Rooster, the spread of El Jannah marks another gateway to the west. The Lebanese chain – known for its garlic sauce and tangy pickles – was founded by Lebanese immigrants Andre and Carole Estephan in Granville in 1998.

It was 11 years before they opened a second store in the south-western suburb of Punchbowl, but the pace has accelerated since. Today, El Jannah has grown into a fully-fledged franchise with more than 40 locations across NSW and Victoria.

Meanwhile, Chargrill Charlie’s, with its golden turmeric quinoa salad and iced teas, rules the roost in the east and the north.

The corner of the internet interested in these things lit up again last week with news that El Jannah was opening its first eastern suburbs store on Belmore Road in Randwick, upsetting the neat lines on Sydney’s chicken map.

“We’ve really, truly broken that Red Rooster Line,” says Adam Issa, head of marketing at El Jannah. “There are a lot of people who have done the pilgrimage to Granville over the years we’ve been open, and Randwick felt like the best location to put a toe into the eastern suburbs.

“We have been getting a lot of comments online from students from UNSW and doctors and nurses from the Randwick hospital saying we want something different to what we eat day-to-day at lunch.”

When Alana Dimou, a Sydney-based food and lifestyle photographer, heard about the new store, she jumped online to update her Substack article, The Four Chicken Frontiers of Sydney, which names Frango as Sydney’s fourth bird borough. The Portuguese chicken chain started in the inner-west suburb of Petersham and occupies middle suburban and south-western territory.

El Jannah’s Randwick store is the sixth outpost to cross the Red Rooster Line since the demarcation was first drawn (Lindfield and Crows Nest are others). It’s a significant breach, but Dimou believes the theory still holds ground.

“The majority of El Jannah stores are still south-west of the Red Rooster Line, and if they do cross it, they stay close to it. They’re pushing the boundary outward,” she says.

The movement of chicken stores has largely gone one way, with only two Chargrill Charlie’s crossing over the line into Olympic Park and Sylvania.

“There’s already so much good chicken in the south-west,” Dimou notes. “There’s a lot of competition and the standard is high. Chargrill Charlie’s would have a lot to contend with.”

In recent years, Lebanese charcoal chicken, which is torn apart by hand and wrapped in bread, has become standard fare in Sydney. “Seeing dishes like fattoush, toum and lefte pickles enter the mainstream has been pretty cool,” says Dimou.

Another south-west Sydney-based Lebanese chain that has followed a similar trajectory is Al Aseel, which opened in Greenacre in 2002. Last year, it expanded beyond its heartland, opening its first north shore location in Chatswood and its first eastern suburbs store in Pagewood. “That’s why El Jannah can push into new areas − because there’s a literal appetite for it,” Dimou says.

El Jannah’s expansion is proof of a growing appreciation of new flavours – and that good food knows no bounds. Issa adds: “Most Australians, we all grew up on rotisserie chicken and that’s what we’ve grown to know and love, and I think this type of chicken, being a charcoal chicken, is a different flavour profile, it challenges what chicken is, especially when you pair it with condiments like pickles and garlic sauce.”

With El Jannah set to open its first northern beaches store in Brookvale this month, its first Brisbane store this year and its first Adelaide store next year, the map that once neatly divided Sydney is struggling to keep up.

El Jannah is now open at 141 Belmore Road, Randwick