The Adventures of Ellery Queen began on CBS radio in 1939 as a one-hour program starring Hugh Marlowe as Ellery, Ted de Corsia (replacing Howard Smith) as Sgt Velie, and Marion Shockley as Nikki Porter. It was cut back to 30 minutes about half-way through its run.

After more than a year off the air the show returned in 1942, now on NBC and with a mostly new cast:

Ellery: Carleton Young
Inspector Queen: Santos Ortega
Sgt Velie: Ted de Corsia
Nikki Porter: Marion Shockley

Listen to complete, digitally restored Ellery Queen radio episodes:

In the fourth season Carleton Young was replaced by Sydney Smith:

In 1945 the show moved to CBS; Barbara Terrell (later Gertrude Warner) replaced Ms Shockley:

In 1947 it was back to NBC, and a new cast:

EQ: Lawrence Dobkin
Inspector Queen: Bill Smith
Sgt Velie: Ed Latimer
Nikki Porter: Charlotte Keane

Herb Butterfield replaced Bill Smith; shortly thereafter Kaye Brinker replaced Charlotte Keane. And eventually Howard Culver took over from Lawrence Dobkin:

Remakes are a staple of movies and tv, and radio was no different. The Ford Theater, a one-hour drama program, dusted off an early EQ script, The Bad Boy, and brought back radio's first Ellery to star in it:

EQ: Hugh Marlowe
Inspector Queen: Santos Ortega
Sgt Velie: Ted de Corsia
Nikki Porter: Charlotte Keane

Australian radio remade a number of US scripts. Charles ‘Bud’ Tingwell took the EQ role, and Wendy Playfair was Nikki: