He is known for his uncredited appearance as Ernst Stavro Blofeld in the James Bond film For Your Eyes Only, as well as for his appearances in the Superman films, Casino Royale, The Dirty Dozen, Flash Gordon, and The Empire Strikes Back.
He played the role of Lobot in The Empire Strikes Back and the German porter at the chateau in The Dirty Dozen.
In television, Hollis took the role of Sondergaard in the Jon Pertwee era of Doctor Who in the story The Mutants, and appeared in The Avengers episode The Cybernauts as a sensei, and in The Superlative Seven as Magwitch.
He also appeared as "Kaufmann" with a young Julie Christie in the BBC classic 'lost series' A for Andromeda.
Notable roles include Magwitch in Great Expectations, Leonard Bast in Howards End, Conan Doyle's Inspector Lestrade and Shakespeare's Bardolph.