Bert Convy was considered for the role. They brought in several unknown actors to read for the role. Ron Sproat, one of the writers, saw Frid's headshot was sent in, knew Frid's stage work from when they attended Yale together, and was anxious to see him. Producer Bob Costello was impressed with Frid when he saw him and decided that was their guy. This was originally a rather small part, remember - just a 13 week shot in the arm. Dan Curtis was away in Europe at that time and back then there was not a quick and easy way for Curtis to be kept up to date with daily auditions at least insofar as seeing photos of actors who were auditioning. So his involvement had to be miminal just by understanding the circumstances of distance where casting Barnabas was concerned.
Frid has has consistently said in interviews and fests that he was called into a writers conference to ask him how he would like to see Barnabas developed and apparently he and the writers were of one mind on that subject. I imagine that situation only happened because Ron Sproat was already familiar with how Frid worked on his characters. Bob Costello has made it clear from his interviews and fest appearance that Curtis had nothing to do with the casting of Frid as Barnabas. or the development of the character.
It's been said that Curtis "made" Frid's career but really when you think about it, who made whose career? Frid didn't pursue TV work after DS. Curtis had become a name because of the success of the series.
Nancy
I read somewhere that Bert Convy tried out for the role before Frid got it. Does anyone know of other noteworthy performers who auditioned for the part?