All 196 suspects are free pending trial. The hearing is due on Thursday near Istanbul.
The suspects include former commander of Turkey's first army, chiefs of navy and air force - who were on duty in 2003. They face up to 20 years in prison if convicted of planning to create chaos for a military takeover in a plot dubbed "Sledgehammer." More than 400 people, including soldiers, are already on trial in a similar but separate case.
Critics say the cases are built on flimsy evidence and illegal wiretaps. The government denies allegations that cases are politically motivated to silence opponents.
In another development, a boiler room explosion at a mosque killed one person and injured 12 others before noon prayers in western Turkey on Tuesday, authorities said. The blast occurred at the Eski Garaj Mosque in the town of Bandirma in Bursa province, south of Istanbul, Mayor Sedat Pekel told the state-run Anatolia news agency.
"We have learned that the boiler exploded due to excessive pressure," Pekel said. «It looks like a war zone." Pekel said two of the injured were in critical condition.
He said the crowd of people were walking in the courtyard toward the mosque after washing themselves for prayers when the blast occurred.
