Designed by Gordon Coppuck with input from John Barnard, the M23 debuted in 1973 and scored 16 Grands Prix victories over its lifespan, along with two drivers' championships (Emerson Fittipaldi in 1974, James Hunt in 1976) and one constructors' championship (1974). The car used a Ford Cosworth DFV engine prepared by Nicholson-McLaren Engines, producing around 490 bhp. Its combination of performance, development longevity, and relative affordability compared to building a bespoke chassis made it attractive to customer operators.
Dave Charlton, a South African racing driver, acquired at least one M23 chassis — chassis M23-2, the car in which Peter Revson won the 1973 British Grand Prix — for use in South African national racing and the non-championship South African Grand Prix events of the period. Charlton used the car at the 1975 South African Grand Prix at Kyalami, finishing 14th.
Gilles Villeneuve made his Formula One Grand Prix debut in 1977 at the British Grand Prix driving an M23, a significant moment given that he would go on to become one of the most celebrated drivers of the following decade.
By 1977, with McLaren developing the successor M26, the works team was phasing out the M23. However, the car remained competitive enough that Hunt and Jochen Mass used the M23E at the start of 1977 before the new car proved reliable, with the M23 still earning pole positions and podium finishes four years after its introduction.
The most unusual privateer application of the M23 was carried out by Australian racing driver John McCormack. After purchasing the Charlton car — Revson's 1973 British Grand Prix-winning chassis M23-2 — McCormack had it modified for Formula 5000 racing by fitting a Repco-modified 4.9-litre Leyland V8 in place of the Cosworth DFV. Former Repco Brabham engineer Phil Irving assisted with the conversion.
The Leyland engine, developing approximately 470 bhp, was chosen because its weight of 160 kg was close to the DFV's 152 kg, minimising the handling disturbance that would have been caused by the heavier Chevrolet (231 kg) or Repco Holden (220 kg) alternatives common in Australian F5000. Although the Leyland gave away power against its rivals, the superior handling balance of the ex-works McLaren chassis compensated. McCormack won the 1977 Australian Drivers' Championship with the converted M23.
McCormack also put the car on pole position for the 1978 Australian Grand Prix — a non-championship event at this period — though a cracked head caused by a blown head gasket, only discovered on the grid before the formation lap, resulted in an early retirement.
The long production run, broad customer availability, and racing longevity of the M23 made it one of the most widely dispersed Formula One chassis of its era. Several examples were preserved: one restored chassis, M23-related to the development programme, is on display in the McLaren collection. The South African and Australian privateer histories illustrate how thoroughly a well-engineered Formula One car could be exploited by independent operators working with limited resources — the M23's structural integrity and the DFV's inherent adaptability being key to its aftermarket appeal.