The company was incorporated on 8 June 1984; it took over Eastern Counties' bus and National Express coach operations from garages in Cambridgeshire and parts of Suffolk (Newmarket and Haverhill) on 9 September 1984.

Meanwhile, Millers Coaches itself was placed under the control of Premier Travel, although the name was retained (and both companies adopted liveries using different colours applied in the same style).

However, following a report by the Monopolies and Mergers Commission, Stagecoach was required to divest itself of its Milton Keynes and Buckinghamshire operations, as well as United Counties' Huntingdon garage.

[citation needed] The operations were acquired by Stagecoach on Monday 31 March 2008 when Cavalier Travel sold their interests in bus services of over 9 seats.

[18] When the Busway opened in 2011, following two years of delays, Stagecoach East operated a fleet of Alexander Dennis Enviro400 bodied Scania N230UD double deckers and Wright Eclipse Urban bodied Volvo B7RLE single decker buses, purchased for £3 million and equipped with specialist equipment for use on the Busway.

[26][27] Introduced in its original form in 1992, the X5 service is operated by Stagecoach East at a 30-minute frequency between Bedford and Oxford via Milton Keynes, Buckingham and Bicester, making use of Alexander Dennis Enviro400 MMC double-deckers.

[28][29] In October 2021, in cooperation with the Cambridgeshire and Peterborough Combined Authority and technology provider Via, Stagecoach East began trial operation of the 'TING' demand-responsive transport system in west Huntingdonshire.

The service, operated by Fenstanton Depot, made use of buses that were not restricted to a timetable and bookable through a smartphone app at a flat fare of £2.