According to both "The Jazz Discography Online" and Brian Rust's "The American Dance Band Discography 1917-1942", Doris Day's first recording session with Les Brown was on Nov. 29, 1940 for Okeh Records. She recorded: "(I Ain't Hep To That Step But I'll) Dig It", "Let's Be Buddies", "While The Music Plays On",
"Three At A Table For Two. As David points out, there are no recordings of Day with the Bob Crosby orchestra (not even radio airchecks, it seems). Interestingly, Vaughan Monroe did play trumpet-including on some of his band's first recordings for Bluebird. 

Thanks, Jeremy. I had forgotten that "The Natural Thing..." was from Trotter's first studio session with Bing. It looks like Trotter's archive which includes annotated musical scores is at the American Heritage Center at the University of Wyoming: https://archiveswest.orbiscascade.org/ark:80444/xv293113?q=John%20Scott%20Trotter
It would fascinating to see what's there and to see who he "farmed" out some of the arranging load to. John Cascales who played tenor sax on the early Kraft shows and a number of Bing Decca recordings (including "Bob White" and "Don't Be That Way") became better known as arranger/composer Johnny Richards. I wonder if some of the more "modern" sounding arrangements used on radio by Bing with Trotter's orchestra were by Richards (1948's "Love Is So Terrific" being a case in point). I know that Trotter used Billy May at times as well an orchestrator for Bing ("On The Atcheson, Topeka and the Santa Fe"). 

Glad that you enjoyed my choices. Like many others on this forum, "That Ol' Spring Fever" is another of my under-rated favourites and it's certainly one of Bing's best 1950s recordings. Part of my enthusiasm for 
"'Sposin'" and "Watermelon Weather" is due to the great arrangements on these recordings (by Roy Bargy and Vic Schoen, respectively). The combination of trombone quartet and rhythm section behind Bing and Peggy on "Watermelon Weather" is unusual and very effective. Bargy makes full use of the Whiteman orchestra's instrumental strength on "'Sposin'" and creates a wonderful setting for the young Bing. 
Sonny Burke's arrangement on "Marrying For Love" is also full of interesting textures especially the use of the low-register clarinets behind the vocal (similar to what Paul Weston and Axel Stordahl did for Tommy Dorsey's singers) and the use of the clarinet-led reed section towards the end of "Marrying..." is also a nice moment reflecting the prevasive Glenn Miller influence as well as the kind of reed section writing Burke did for Artie Shaw and Bob Crosby.

Many thanks for your greetings, Graham. As a member of the ICC since 1998, I've enjoyed your many articles in "Bing" magazine over the years! This isn't a Bing-related question but did you hear Artie Shaw when he toured Australia in 1954. That was the last public playing he did.

You've been listening to "From Monday On" I'd imagine. A great tune with great lyrics by Bing. Until I heard the Rhythm Boys version, I had no idea that the verse had lyrics as well. In the 3 Paul Whiteman recordings, the verse is played as a violin section "soli". We played this arrangement twice on CBC Radio in Vancouver back in 1995-96. The parts for "From Monday On" housed at the Whiteman Collection at Williams College (Mass.) barely resembled the famous Whiteman recordings. I had the pleasant task of transcribing the arrangement from the recorded sources. Since we didn't have a vocal group on our CBC broadcast, I orchestrated the vocal intro for the violin section. 
Matty Malneck's arrangement on this song is one of his best (along with "Mary").

Hi Jim, I read with interest your query about a Johnny Mercer discography. 
The "Jazz Discography Online" (which is a subscriber supported service) does have a relatively complete Mercer discgraphy encompassing his more jazz-based work. I noticed that the Glendale recording you mention only lists the 1983 release date and no personnel details. Your guess about the early-mid 1960s date for the Glendale recordings does make sense. Please contact me privately if you would like more information.