 O'Neill was a Fellow of the Royal Astronomical Society and Royal Geographical Society, as well as an Honorary Corresponding Member of the Scottish Geographical Society.He was the 1882 recipient of the Royal Geographical Society's Back Award and the 1885 recipient of their Gold Medal.Some of his published works include, "Journey from Mozambique to Lake Shirwa, and discovery of Lake Amaramba", and 
"Astronomical observations between Mozambique coast and lake Nyassa".