The bank, which only survived the 2008 global financial crisis with government help, said Francois Gouws and Yassine Bouhara, co-heads of the Global Equities unit, had stepped down.
"Their resignations come as they assume overall responsibility for the effective management of the Equities business," a statement on the group's website said.
"In addition, appropriate disciplinary action will be taken against other individuals in the Equities business as a result of the incident," it said.
"UBS also expects to take disciplinary action against responsible staff in other functions."
Mike Stewart, previously at Bank of America Merrill Lynch, will become sole global head of Equities at UBS, it added.
Grübel resigned last month after Kweku Adoboli, a UBS trader, was accused of a €1.7 billion fraud which rocked the bank and the financial markets at a time of great stress from the eurozone debt crisis.
UBS said at the time it would "fully support" an independent investigation into the rogue trading and would ensure that "mitigating measures" were implemented to prevent such incidents from recurring.