In the 50's, 60's, and 70's, a common operation in television was the anthology, or, "wheel" series, in which series were rotated under a common title.
NBC's The Bold Ones lasted four seasons (1969-73), anchoring the back end of the network's Sunday lineup. Universal had several of these "wheel" series at NBC over the course of a decade, including the network's Mystery Movies and The Name of the Game.
In the course of the four seasons, there were four different features:
The Protectors, aka The Law Enforcers, lasted just the first season. Leslie Nielsen plays a detective often at odds with the district attorney (Hari Rhodes, ex-Daktari).
The Senator replaced Protectors, but also lasted 1 season (1970-1). Hal Holbrook had the title role.
The Lawyers got a head start with a pair of pilot movies produced during the 1968-9 season. Singer-actor Burl Ives (ex-OK Crackerby), still better known for his work on Rudolph the Red Nosed Reindeer, heads up the law firm with his partners being played by Joseph Campanella (ex-Mannix, Batman) and James Farentino.
The Doctors, meanwhile, drew the rub of a crossover with Ironside, and maybe that's because it came from the same production company (Harbour). EG Marshall (ex-The Defenders) was paired with John Saxon and David Hartman. Saxon left 3 episodes into the 4th season, replaced by Robert Walden, who is better known for his later work on Lou Grant.
A few years back , Retro brought back Bold Ones to air on weekends, but it didn't last long. Current cable whereabouts are unknown.
We'll start with a season 1 intro, narrated by actor Marvin Miller (ex-The Millionaire):
And, just for kicks, here's a rare promo video for the series, uploaded by Matt The Saiyan, and narrated by Hugh Downs (Concentration, The Today Show).
As you can see, this was taken from a network fall preview show, with Downs joined by Joe Garagiola.
Now, if only a DVD could be made available......