The Scottish Motor Traction Company Ltd. (trading as "SMT") was formed in 1905, and expanded quickly through a series of takeovers to become the principal bus operator in south east Scotland.

In the Edinburgh area this history resulted in SMT/Eastern Scottish retaining the right to carry passengers within the city boundary (contrast Glasgow where only pickup outward and set-down inward were permitted).

Stark's had operated some of its services jointly with Scottish Omnibuses for some years, and a proportion of its fleet was already painted in SMT livery.

When the Baxter's business was acquired, adverse public reaction to the repainting of buses into Scottish Omnibuses livery led to a decision to retain the Baxter's identity and blue livery for buses based at Victoria depot and used on town services around Airdrie and Coatbridge.

The Stark's livery, a lighter shade of green than that used by Scottish Omnibuses, was retained for buses at Dunbar and North Berwick.

Both local identities disappeared in the late 1970s when the SBG's new corporate fleetname style was introduced ("Eastern SCOTTISH", with a saltire logo).

Initially, SBG coaches used on express services to London received a special blue and white livery with "SCOTTISH" branding; in the early 1980s most other express services were branded "Scottish Citylink" with a two-tone blue and yellow livery.

Changes to depots over the years comprised: In preparation for deregulation in 1986, and eventual privatisation, the Scottish Bus Group was reorganised in 1985.

Some routes were operated by a fleet of 70 Dodge minibuses, whilst others used double deck buses, notably 25 secondhand ex-South Yorkshire Transport Volvo Ailsa B55s with Irish-built Van Hool-McArdle bodywork.

Despite competition between the two operators, bitter "bus wars" that broke out in other cities and towns across Scotland were largely avoided, and Eastern did not persevere with loss-making operations, but settled for economy by reducing use of St. Andrew's Bus Station by running through Edinburgh city centre to destinations such as Charlotte Square, Haymarket, Clermiston and Silverknowes, and connecting traditional routes such as ones to Balerno and Wallyford end-to-end to create new cross-city links which in some cases competed with those of LRT.

This was due in large part to initiatives such as the City Sprinter minibus scheme, which had quickly expanded into a considerable network of high-frequency routes.