The original Minor MM series lasted from 1948 until 1953. It included a pair of 4-seat saloons, 2-door and 4-door, and a convertible 4-seat Tourer. The front torsion bar suspension was shared with the larger Oxford MO, as was the almost-unibody construction. Although the Minor was originally designed to accept a flat-four engine, with four distinctive gaps in the engine bay to accommodate it, late in the development stage it was substituted for a 0.9 L (918 cc/56 in³) side-valve straight-4 producing 27.5 hp (21 kW) and 39 lbf·ft (53 N·m) of torque. This little engine pushed the Minor to just 64 mph (103 km/h) but delivered 40 mpg (5.9 L/100 km).
When production of the first series ended, just over a quarter of a million had been sold with a surprising 30% being the convertible Tourer model. In 1952, the Minor line was updated with an Austin-designed 0.8 L (803 cc/49 in³) overhead valve A-Series engine replacing the original sidevalve unit. The engine had been designed for the Minor's main competition, Austin's A30, but became available as Austin and Morris were merged into the British Motor Corporation. The new engine felt stronger, though all measurements were smaller than the old. The 52 second drive to 60 mph (97 km/h) was still calm, with 63 mph (101 km/h) as the top speed. Fuel consumption also rose to 36 mpg (6.5 L/100 km).
An estate version was introduced, known the Traveller (a Morris naming tradition for estates, also seen on the Mini), along with van and pick-up versions. The Traveller featured an external structural ash (wood) frame for the rear bodywork, with two side-hinged rear doors. The frame was varnished rather than painted and a highly visible feature of the bodystyle. Rear bodies of the van versions were all steel. The 4-seat convertible and saloon variants continued as well.
The car was again updated in 1956 when the engine was increased in capacity to 0.9 Ltr (948 cc/57 in³). The two piece split windscreen was replaced with a curved one-piece one and the rear window enlarged. At the same time the semaphore-style trafficators were replaced by the more modern flashing direction indicators then becoming the norm for the UK market.
An upmarketcar based on the Minor floorpan but with larger BMC B-Series engine was sold as the Riley One-Point-Five/Wolseley 1500 beginning in 1957: a version, with tail fins added, of this Wolseley / Riley variant was also produced in Australia as the Morris Major.
In 1961 the Morris Minor became the first British car to sell over 1,000,000 units. To commemorate this event, a limited edition of 350 two-door saloons were produced with distinctive lilac paintwork and a white interior. Also the badge name on the side of the bonnet was modified to read "Minor 1,000,000" instead of the standard "Minor 1000".