In 1967, McVie heard that Silvester and Webb were forming a blues band, to be called Chicken Shack, and were looking for a pianist. She contacted them and was invited to join the band as pianist, keyboard player and backing vocalist. Chicken Shack's debut release was "It's Okay with Me Baby", which was written by and featured McVie. She stayed with the band for two studio albums, and her genuine feel for the blues became evident in her Sonny Thompson-style piano playing and her authentic "bluesy" voice.

Chicken Shack had a hit with a cover of Ellington Jordan's "I'd Rather Go Blind", which featured McVie on lead vocals.^[23] McVie received a Melody Maker award for UK's best female vocalist in 1969 and again in 1970. She left Chicken Shack in 1969, having married Fleetwood Mac bassist John McVie a year earlier, feeling that she would not see her husband if they were in different bands.