During his tenure as Bishop, O'Leary continued to focus on projects that had flourished under his brother.
Also, the Sisters of St. Martha of Prince Edward Island continued to grow and officially became a congregation in 1923.
The Sisters took over the tasks of managing the Charlottetown Hospital and St. Vincent's Orphanage after the Grey Nuns of Quebec returned to their native province after 46 years of service on Prince Edward Island.
Following his release from hospital in 1929, the Bishop went for a period of rest at his brother's home in Dayton, Ohio.
His funeral mass was held at St. Dunstan's Basilica in Charlottetown and was presided over by the late Bishop's brother, Archbishop Henry O'Leary of Edmonton.