The Jedi Assembly was a loose administrative body established within the Jedi Order on Ossus. Comprised of the wisest Jedi Masters of the era, the body met daily to sit and meditate in each others' presence. In addition to discussing the goings on within the Order, they advised Jedi Knights and offered counsel to those who sought it. After many of the assembly's members were slain during the pogrom of 3996 BBY, the body was disbanded. Not long after, the Assembly was reconvened as the Jedi High Council, a formal executive body of the Order which would lead the Jedi on and off until its final dissolution in 19 BBY.
This assembly was made up of several trusted Jedi Masters who met on Ossus and on Coruscant daily to meditate and discuss the philosophies of the Jedi. Set up to create a loose hierarchy in the Jedi Order, the Assembly was made up of Jedi such as Ood Bnar, Vodo-Siosk Baas, and Thon and led by Master Odan-Urr for 600 years. Meeting in a circular chamber, the room was devoid of any furnishing save for a jut of stone at the chamber's center. Embedded in the stone was a massive Force crystal which helped focus the Force energies in the room.
In 3996 BBY, many of the Assembly's members were viciously slaughtered by either their own students during the pogrom of Exar Kun or in the attack preceding the devastating Cron Supernova which left Ossus relatively uninhabitable. Ten years after Ossus was devastated, Master Nomi Sunrider called for a convocation of all Jedi on Exis Station where she took the lead on the future of the Order. Establishing a new body to replace the Assembly, a new Jedi High Council was created to govern the order more strictly in hopes of preventing more Jedi from falling to the dark side of the Force.