Born in Borrisokane, County Tipperary, Ireland on 18 February 1861, Timothy Quinlan emigrated to Western Australia with his parents in 1863.

In 1882, Quinlan leased the Shamrock Hotel in Perth from Daniel Connor, an expiree convict who had become one of the wealthiest men in the colony.

Quinlan's brother-in-law, Michael O'Connor, also served a term in the Legislative Assembly, where he represented the seat of Moore.

Quinlan became embroiled in a controversy regarding provision of state aid to private schools, which he and fellow Catholic MLAs Thomas Molloy and Alfred Canning supported.

The Catholic Vicar General, Father Anselm Bourke, established the Education Defence League with their assistance.