The film marks a reunion for Stanwyck and William Holden (McDonald "Don" Walling). Stanwyck was the star of Golden Boy (1939), and Holden was a newbie when he appeared in the title role. As the film rushes came in, Harry Cohn made it clear that was not satisfied with Holden's performance, and was going to replace him. Stanwyck defended him, and worked with him to improve his performance (Check out this TCM article for that story and others). Golden Boy became Holden's breakthrough role. Stanwyck and Holden remained friends, and he tried for years to convince the Academy to present her with an Honorary Oscar for her body of work. Ultimately, he did succeed, but by the time she received the award, he had died. In this video, you can will see Holden's praise of Stanwyck at the 1977 Oscars, and her moving acceptance speech in 1983 as she expresses her affection for her "Golden Boy".
Also remarkable is Fredric March as Loren Phineas Shaw, the chief financial officer for the company. Shaw's economies have put him at odds with Don, having advocated for and won approval of a cheap brand of furniture that, while enhancing the company's coffers, proves an embarrassment to the firm's employees and to many members of the board. March gives Shaw a number of small tics that quickly define his character for the viewer - watch how he constantly wipes his hands. His Shaw is a character you cannot like, and March is not afraid to make him, while not quite a villain, at the very least an unattractive individual.
Also very interesting is the credit role. We are all used to credits which show brief names of the characters' next to that of the actors, but Executive Suite gives us the characters full names - names that were not used within the film. We learn that Don Walling's name is actually MacDonald, and that his wife's maiden name is Blemond. Again, the character's begin to have a life outside the frame of the story - they have a past. They will have a future.
We were unfamiliar with Lucille Knoch, who the end credits inform us was Mrs. George Nyle Caswell (the wife of Louis Calhern's manipulative George Caswell - another masterful character creation), not his mistress, as we all had assumed. Ms. Knoch quite good in this part. She had a relatively short career - this was possibly the largest role she ever had. She seems to have stopped acting after 1957; she died in 1990.
We'll leave you with a trailer from the film - an introduction to all the characters, including Stanwyck's Julia Tredway: