Technical Ecstasy And Never Say Die! (1976–1979)

Black Sabbath began work for their next album at Criteria Studios in Miami, Florida, in June 1976. To expand their sound, the band added keyboard player Gerry Woodruffe, who also had appeared to a lesser extent on Sabotage. Technical Ecstasy, released on 25 September 1976, was met with mixed reviews. For the first time the reviews did not become more favorable as time passed, two decades after its release AllMusic gave the album two stars, and noted that the band was "unravelling at an alarming rate". The album featured less of the doomy, ominous sound of previous efforts, and incorporated more synthesisers and uptempo rock songs. Technical Ecstasy failed to reach the top 50 in the US, and was the band's second consecutive release not to achieve platinum status, although it was later certified gold in 1997. The album included "Dirty Women", which remains a live staple, as well as Bill Ward's first lead vocal on the song "It's Alright". Touring in support of Technical Ecstasy began in November 1976, with openers Boston and Ted Nugent in the US, and completed in Europe with AC/DC in April 1977. In November 1977, while in rehearsal for their next album, and just days before the band was set to enter the studio, Ozzy Osbourne quit the band. "The last Sabbath albums were just very depressing for me", Osbourne said. "I was doing it for the sake of what we could get out of the record company, just to get fat on beer and put a record out." Former Fleetwood Mac and Savoy Brown vocalist Dave Walker was brought into rehearsals in October 1977, and the band began working on new songs. Black Sabbath made their first and only appearance with Walker on vocals, playing an early version of the song "Junior's Eyes" on the BBC Television program "Look! Hear!". Osbourne initially set out to form a solo project, which featured ex-Dirty Tricks members John Frazer-Binnie, Terry Horbury, and Andy Bierne. As the new band were in rehearsals in January 1978, Osbourne had a change of heart and rejoined Black Sabbath. "Three days before we were due to go into the studio, Ozzy wanted to come back to the band," Iommi explained. "He wouldn't sing any of the stuff we'd written with the other guy, so it made it very difficult. We went into the studio with basically no songs. We'd write in the morning so we could rehearse and record at night. It was so difficult, like a conveyor belt, because you couldn't get time to reflect on stuff. 'Is this right? Is this working properly?' It was very difficult for me to come up with the ideas and putting them together that quick."

The band spent five months at Sounds Interchange Studios in Toronto, Canada, writing and recording what would become Never Say Die!. "It took quite a long time," Iommi said. "We were getting really drugged out, doing a lot of dope. We'd go down to the sessions, and have to pack up because we were too stoned, we'd have to stop. Nobody could get anything right, we were all over the place, everybody's playing a different thing. We'd go back and sleep it off, and try again the next day." The album was released in September 1978, reaching number twelve in the UK, and number 69 in the US. Press response was again unfavourable and again did not improve over time with Eduardo Rivadavia of AllMusic stating two decades after its release that the album's "unfocused songs perfectly reflected the band's tense personnel problems and drug abuse." The album featured the singles "Never Say Die" and "Hard Road", both of which cracked the top 40 in the UK, and the band made their second appearance on the Top of the Pops, performing "Never Say Die". It took nearly 20 years for the album to be certified Gold in the US.

Touring in support of Never Say Die! began in May 1978 with openers Van Halen. Reviewers called Black Sabbath's performance "tired and uninspired", a stark contrast to the "youthful" performance of Van Halen, who were touring the world for the first time. The band filmed a performance at the Hammersmith Odeon in June 1978, which was later released on DVD as Never Say Die. The final show of the tour, and Osbourne's last appearance with the band (until later reunions) was in Albuquerque, New Mexico on 11 December.

Following the tour, Black Sabbath returned to Los Angeles and again rented a house in Bel Air, where they spent nearly a year working on material for the next album. With pressure from the record label, and frustrations with Osbourne's lack of ideas coming to a head, Tony made the decision to fire Ozzy Osbourne in 1979. "At that time, Ozzy had come to an end", Iommi said. "We were all doing a lot of drugs, a lot of coke, a lot of everything, and Ozzy was getting drunk so much at the time. We were supposed to be rehearsing and nothing was happening. It was like 'Rehearse today? No, we'll do it tomorrow.' It really got so bad that we didn't do anything. It just fizzled out." Drummer Bill Ward, who was close with Osbourne, was chosen by Tony to break the news to the singer. "I hope I was professional, I might not have been, actually. When I'm drunk I am horrible, I am horrid," Ward said. "Alcohol was definitely one of the most damaging things to Black Sabbath. We were destined to destroy each other. The band were toxic, very toxic."