Berkshire Hathaway has disclosed a $528.7 million stake in Verizon, or 11,022,743 shares.
Dan Loeb's Third Point LLC also disclosed a stake in the telecom giant.
Verizon shares were up more than 1% after hours Thursday.
In its latest 13-F filing, the Warren Buffett-helmed firm also said it had upped its stakes in Walmart, IBM, DaVita Healthcare and U.S. Bancorp.