One thing I was reminded of once again, in watching The Rockford Files season 3, is how good Gretchen Corbett was as Jim's lawyer Beth Davenport. She was, indeed, one of the few really good women characters on hour-long TV in the testosterone-laden '70s: smart, attractive, funny, a real match for James Garner in every scene they had together, and always believable. In her scenes in the episode "So Help Me God," she's not your typical TV super-lawyer who knows everything about everything; she admits (in the scene before this one) that she doesn't know a lot about the grand jury process, has to bone up on the subject before Jim testifies, and just generally seems like one of the few TV lawyers who has to look something up before she cites it.
Corbett's Wikipedia entry is quite good. She was, as the entry says, one of the last people signed by Universal in the old studio-system style. Universal was the last studio to try and maintain that type of operation; they had a big film operation and an even bigger TV production operation, and they would sign actors, directors and technicians who could be used for all their TV projects and then moved into feature films. That's how Steven Spielberg got started (first episodic TV, then TV movies, then features, all for Universal). But maintaining the system depended on having lots of shows on the air, and by the mid-'70s networks were buying fewer of the kind of L.A.-based action and mystery shows that Universal specialized in. So the Universal studio system collapsed like all the others.
I'm not sure exactly why Corbett left The Rockford Files after the fourth season; it's usually written that she left over a salary dispute, while others have written that it was simply that her contract with Universal had expired. I'm inclined to put the two explanations together and speculate that once her contract ran out, she demanded to be paid not as a studio contract player on assignment but as a semi-regular on a hit show. The difference between the two salary levels was probably pretty big.
She did do a few guest roles after that, but she was never a regular on a series again. I'm assuming that she probably mostly went back to stage work. (She now lives in her native Portland, Oregon, where she runs a non-profit theatre organization for underprivileged children.) But you would have thought Universal or NBC or somebody would have thought of her as a candidate for the lead in a series; in fact, Beth is one of the few characters who I really thought would have made a viable spin-off character.
Final note: Corbett got the part on Rockford soon after doing a major guest role on an episode of Columbo (the one with Robert Conrad as a murderous health guru). Universal may have given her the role of Beth based on that Columbo, though the thing you wonder in that scene is why she's wearing a bikini on what doesn't appear to be a particularly pleasant day. But that's the joy of '70s Universal shows -- they shot all around L.A., in good, bad and mediocre weather, and the shows may not look beautiful but they're like a guided tour of the city.
Oh, and speaking of Beth, there's an episode of Hunter written by Stephen J. Cannell (the only episode of that show he wrote himself) that features Hunter's lawyer, who is a blatant knock-off of Beth -- she has all the Beth lines, talks to Hunter's boss the way Beth talked to Dennis Becker, and she gets Hunter off by citing a bunch of precedents that she later admits she made up on the spot. The character never appeared again, but either it was an attempt to come up with a new Beth character for the '80s, or Cannell just rewrote an old Beth-Jim-Dennis scene out of time constraints. (Adding to the retro-Rockford feel, Joe Santos is in that Hunter episode basically playing Dennis Becker under a different name.)