Coates appeared only in the first season of The Adventures of Superman from 1952 and the film, Superman and the Mole Men.
I am a fan of all Loises, and as part of the legion of Loises, Ms. Coates folds a special place here at The Signal Watch. Her Lois was quite a bit different from Noel Neill's take. Coates tended to play a bit more into the streetwise, tough newspaper writer persona that would circle back around with some other actors to play the part.
She left pretty quickly, but one does not play Lois and not get included in the Superman mythos. As is the tradition, she returned to a different incarnation of Superman, appearing on Lois and Clark: The New Adventures of Superman in the first year as Lois' mother, Ellen Lane.
Of course, Coates was infinitely more than her brief Superman appearances. She has 145 appearances listed on IMDB, and spanned 50 years in the business (including a lengthy break).
Let's salute Ms. Coates and remember her for being a terrific part of the Superman legacy!