A Hamburg-based performer, Grützner dubbed Neil Hamilton as Commissioner Gordon on Batman, Alan Oppenhimer on The Six Million Dollar Man, Frank Sinatra in the documentary The Spencer Tracy Legacy: A Tribute by Katharine Hepburn, Herb Edelman on The Golden Girls, Bruce Kirby in three Columbo installments, and Philip Baker Hall in Three O'Clock High. Cartoon roles included Poet Smurf on The Smurfs, Mayor White on Doug, and MAD agents on Inspector Gadget. He was heard in German Disney records in many roles, including Goofy, Colonel Hathi, Mr. Smee, Uncle Albert in Mary Poppins, and kings in Cinderella and Sleeping Beauty. Other audio roles included Wimpy in Popeye cassettes, various roles in The Three Investigators and The Famous Five series, and Ming's priest on a Flash Gordon record.
Grützner was active on German radio, appearing in fifteen episodes of the crime anthology Die Jagd nach dem Täter from 1957 to 1962 (usually as police inspectors). He later played Lt. Ybarra in a 1981 radio version of Raymond Chandler's Red Wind. On German TV, he appeared in Die Gentlemen bitten zur Kasse (1966), a three-part depiction of the 1963 "Great Train Robbery," as Sgt. Robbins. He played episodic roles on Graf Yoster gibt sich die Ehre (with Wolfgang Völz), Cliff Dexter, Tatort, and Unheimliche Geschichten.