Grainger entered into partnership with Phillip Kennedy and John Little. Grainger, Kennedy & Little practiced as architects and civil engineers and had an office at 123 Queen Street in central Melbourne.

This period of his professional life began with a quite prestigious success. Shortly after his arrival in Melbourne he won first prize in a competition for a design for a northern wing to Melbourne’s Town Hall. His firm was also responsible for the design of St Michael's Catholic Church in North Melbourne.