Jeff Howard tapped out on Monday evening "with immediate effect", the day before the company's first-half results announcement on Tuesday.
Mr Howard was the former head of its newly acquired Seven West Media assets and had only been in his new position for just under seven weeks.
While admitting that the sudden change was "significant", Southern Cross executive chair Heith Mackay-Cruise said it was a matter of speeding up the $400 million-plus merger to drive revenue and savings.
The existing Southern Cross Austereo audio business, which includes the Triple M, Hit and regional radio networks and podcast platform LiSTNR, is being integrated with Seven West, which includes Network Seven and The West Australian newspapers and digital platforms.
"So the key now is accelerating the delivery of that strategy and positioning our group to more quickly realise the benefits of our merger, and that culminated in changes to the leadership team," Mr Mackay-Cruise told analysts during an earnings briefing.
The overall group delivered underlying earnings - before interest, tax, depreciation and amortisation - of $106 million, down 14.5 per cent, in the first half of 2025/26 on a pro-forma basis.
Revenue was also down, by 1.5 per cent, to $1 billion, due to ongoing challenges in the advertising market, particularly for television and print.
As Southern Cross kicks off a global search for a new CEO, its long-term chief operating officer John Kelly is stepping up to head the core television and audio businesses and may be in the line-up for the top job.
The audio business generated interim underlying earnings of $40 million, up 28 per cent on the previous first half.
The TV and publishing assets reported underlying earnings of $67 million, down 27 per cent, as previously announced by former owner, the Stokes-family controlled conglomerate SGH.
Mr Mackay-Cruise played up access to regional Australia, saying the group had 73 per cent of all radio listeners and 46 per cent of all television viewers.
At the same time, Seven's free-to-air TV audience was growing better than the market as a whole, streaming minutes for its 7 Plus on demand channel was up 62 per cent year on year, with sport - especially AFL and cricket - a key driver.
More than 20 per cent of West Australians were reading at least one edition of the newspapers under The West Australian arm, Mr Mackay-Cruise said, and the digital platform had an audience of 5.7 million.
The West's flagship The Nightly online news service was catching eyes beyond the border, he stressed.
"It is truly national, with more than 80 per cent consumption outside of Western Australia," he added.
The group is aiming for cost savings of $30 million in the next 2026/27 financial year.
While it did not specifically say which business units would be affected, Mr Mackay-Cruise pointed to cross-promotion as TV accelerated growth in its audio and digital audiences.
Southern Cross is targeting pro-forma group revenue of $1.91-$1.92 billion for the 2025/26 financial year and a dip in group underlying earnings to $200-$220 million, from $233 million in 2024/25.
No interim dividend will be paid as the group focuses on paying down almost $340 million in net debt.
Southern Cross shares fell by 3.76 per cent to 64 cents in morning trading.
