George Bernard O'Neill was born on 17th July 1828 in Dublin the ninth of fifteen children of Bernard and Sarah O'Neill. The O'Neills left Ireland in the late 1830s and settled at Woolwich Arsenal in Kent where Bernard O'Neill was an Ordnance storekeeper. George studied art at the Royal Academy Schools where he started exhibiting in 1847 at the age of 19 and his career as an artist took off when he submitted "The Foundling" to the 1852 Royal Academy Summer Exhibition. In 1857 he married Emma Stuart Callcott and over the next twelve years she bore him seven children. In 1863 the O'Neills leased "Old Wilsley" in Cranbrook as a summer residence next door to Emma's cousin the painter John Callcott Horsley - both George and John being attracted to the artist colony being formed in Cranbrook. The O'Neills remained there until 1886, making many changes to the residence and laying out the gardens.

Frederick Daniel Hardy, George Hardy, Thomas Webster, George Bernard O'Neill, John Callcott Horsley and Augustus Edwin Mulready were an informal group of six professional painters known as the Cranbrook Colony that thrived in Cranbrook in the latter half of the nineteenth century. They were a close association of colleagues and friends, and, in the case of the Hardy brothers and G.B. O'Neill, distant relatives. All six were "Genre" painters depicting scenes from daily life, either real or imaginary and, through their work, we have an accurate depiction of the people and homes in the Cranbrook area during the Victorian age. Often the Colony used their children, families and friends as models with the Hardys and Webster focused on rustic interiors and O'Neill and Horsley on picturesque historic architecture. The six painters, who occupied The Old Studio in the High Street, were prolific in their work and exhibited extensively at the Royal Academy and the British Institution.

George continued to work as a painter into the twentieth century in London where he died at the age of 89 on 23rd September 1917