One of the reasons WKRP was never a huge hit during its original run on CBS, is that the network kept moving the show's time slot. Here's exactly when, why, and how they did it. I get the sense that the show only lasted as long as it did is because it was from one of CBS' most prestigious producers -- MTM Productions -- which also supplied "The White Shadow" and "Lou Grant" during this same time. I have no specific data to back this up, but WKRP probably performed well enough to come in second in its time slot, which was good enough for the network.
WKRP started out Mondays at 8, getting killed by "Little House on the Prairie." (This is referenced in the "Real Families" episode from season 3). After 6 episodes, the show was put on hiatus to retool. The emphasis on Andy Travis went away, stories became more about office politics and less about radio, and they added the bullpen set (with Les' desk). The show also got a great new slot, at 9:30 on Mondays, right after MASH (which was the #7 show on TV).
WKRP stayed there through the first 10 shows of season 2, then was bounced back to 8pm to again get killed by both #16 "Little House" and #3 "That's Incredible." The reason for the move was to make way for the Lynn Redgrave/Wayne Rogers vehicle, "House Calls," which premiered December 17. WKRP had its only year-end placing in the Top 30 for season 2, coming in at #22.
For season 3, the show got moved to Saturdays at 8pm. But unlike a decade earlier -- when CBS' Saturday night lineup was one of the best ever -- WKRP was leading into "The Tim Conway Show" at 8:30 and then a movie at 9pm... a movie which was up against #5 "The Love Boat" and #17 "Fantasy Island." So it seems that no one was watching TV until 9pm. WKRP found itself against Barbara Mandrell's show, and a constantly changing slate on ABC which included two programs on their last legs ("Charlie's Angels" and "Eight Is Enough") and the short-lived TV adaption of "Breaking Away."
For its final season, the show started off on Wednesdays at 8:30pm, against the second halves of the cult favorite "The Greatest American Hero" and #21 "Real People." WKRP's lead-in was the wildly unpopular Barnard Hughes vehicle, "Mr. Merlin." After 10 shows, Merlin was bounced to Mondays and WKRP moved up to 8pm. Another 6 shows aired and then they were moved to 9pm, against #24 "Facts of Life" and the first half of #26 "The Fall Guy." That's where the show aired its remaining shows. Reruns filled out the CBS run on Mondays at 8:30pm -- again opposite the Top 30 "Little House" and "That's Incredible," and just before #9 MASH. I'm not exactly clear on this next part, but either the final first-run episode (April 21, 1982) or the final CBS-aired show (sometime in the summer) came in #7 for the week! It's more likely the latter -- Howard Hesseman always felt that once audiences could finally find them, people spent the summer catching up on episodes they didn't get to see earlier in the season. Note that WKRP was performing so poorly that spring that two episodes were hastily pre-empted and didn't run until August and September.
On a side note, I've often wondered if there was an additional reason for WKRP (and Lou Grant) being canceled in the spring of 1982: MTM head Grant Tinker became Chairman of NBC in the summer of 1981. Why keep a show on from the man running a rival network? CBS did premiere "Newhart" in the fall of 1982, but I believe Bob's contract specified his show had to air on CBS. And considering it was almost guaranteed to be a hit, I'm sure CBS could overlook the Tinker/NBC connection. Tinker himself stepped down from MTM at some point to avoid conflict of interest, especially since NBC premiered MTM's "Hill Street Blues," "St. Elsewhere," "Remington Steele," and "Bay City Blues" between 1981 and 1983.
