In the early 1980s, teams like Renault, Ferrari and Brabham were using 1.5-litre turbocharged engines in favour of the 3.0-litre naturally aspirated engines that had been standard since 1966. Having seen in 1982 the need for a turbo engine of their own, Dennis had convinced Williams backer Techniques d'Avant Garde (TAG) to fund Porsche-built, TAG-branded turbo engines made to Barnard's specifications; TAG's founder Mansour Ojjeh would later become a McLaren shareholder. In the meantime, they continued with Cosworth engines as old rival Lauda came out of retirement in 1982 to drive alongside Watson in that year's 1B development of the MP4. They each won two races, Watson notably from 17th place on the grid in Detroit, and at one stage of the season McLaren were second in the constructors' championship. As part of a dispute with FISA, they boycotted the San Marino Grand Prix. Although 1983 was not so fruitful, Watson did win again in the United States, this time from 22nd on the grid at Long Beach.
Having been fired by Renault, Prost was once again at McLaren for 1984. Now using the TAG engines, the team dominated, scoring 12 wins and two-and-a-half times as many constructors' points as nearest rival Ferrari. In the Drivers' Championship, Lauda prevailed over Prost by half a point, the narrowest margin ever. The McLaren-TAGs were again strong in 1985; a third Constructors' Championship came their way whilst this time Prost won the Drivers' Championship. In 1986, the Williams team were resurgent with their Honda engine and drivers Nigel Mansell and Nelson Piquet, whilst at McLaren, Lauda's replacement, 1982 champion Keke Rosberg could not gel with the car. Williams took the Constructors' Championship, but for Prost, wins in San Marino, Monaco, and Austria combined with the fact that the Williams drivers were taking points from each other meant that he retained a chance going into the last race, the Australian Grand Prix. There, a puncture for Mansell and a precautionary pit stop for Piquet gave Prost the race win and his second title, making him the first driver to win back-to-back championships since Jack Brabham in 1959 and 1960. In 1987 Barnard departed for Ferrari to be replaced by Steve Nichols (who himself joined Ferrari in 1989). In the hands of Prost and Stefan Johansson, though, Nichols's MP4/3 and the TAG engine could not match the Williams-Honda.