In the Autumn 1978 ratings, KZAP had a 2.7 12 plus share as a Progressive Rock station. It's slightly more mainstream competion KSFM had a 4.7 12 plus share.
In January 1979 KZAP's new owners flipped to Mainstream AOR as a Burkhart-Abrams Superstars client. Their ratings soared to 8.1, while KSFM fell to a 3.1 12 plus shart.
In September 1979, KSFM flipped from Progressive Rock to "Mass Appeal" CHR. In the Spring of 1980, KZAP then rose to number one in the market with a 15 twelve plus share. It was the only commercial rock station in town at that time.
In 1981, KROY-FM (96.9) and AM (1240) moved into a more Mainstream AOR format. They got decent shares in the 4s. KZAP remained in the upper 8s and lower 9s.
In 1984, KROY-FM dropped AOR for Soft AC. KZAP's ratings remained high (8s), but did not match their 1980-81 Success.
On Friday, January 10, 1986, KPOP (93.5) flipped from CHR to AOR as KDJQ and eventually KRXQ. Their ratings remained in the 2s and 3s, 12 plus until they moved to the 93.7 frequency in July 1988 and upgraded their signal from 3kw to 25kw. "93Rock" skewed towards younger listeners with mainstream hard rock. Their rise in ratings are well-detailed on Alex Cosper's website. KZAP's ratings slide began with the debut of 93 Rock at a Metro-Grade signal.
KSEG's debut in November 1990 pulled the upper demos away from KZAP. By the end of 1991, KZAP had a 2.1 share. On Sunday, January 20, 1992, KZAP went country as "Fresh Country 98." KZAP's last song was "Christo Redentor" by Harvey Mandel. That was the same song KZAP used to sign on each morning with when they debuted back in November 1968. Prior to their sign-off song, KZAP had a pre-recorded Sunday evening special known as "Charlie's CD Cellar," where complete releases were played back. Ted Nugent's "Cat Scratch Fever" was cut off in mid-stream, so "Christo Redentor" could be played for the last time prior to the midnight format switch.
In August 1998, 93 Rock moved to the 98.5 frequency, and the rest is history. I wonder if any other broadcaster will attempt to challenge Entercom's KRXQ for its share of the audience? We live in unique times.