He grew up with five siblings in Podersdorf and Loretto, where he attended elementary school, before moving to Eisenstadt.

After successfully completing his law studies, Steiner entered the service of the Burgenland state government as a contract employee in 1991.

Between 1991 and 1996 he was secretary of the ÖVP group in the state Landtag, and from 1996 to 2000 he worked in the office of the provincial governor's deputy.

[3] The Proporz system was abolished in Burgenland in 2014, and after the 2015 election the ÖVP was relegated to opposition for the first time since 1945.

The party recorded a small swing in its favour, but did not recover the losses it had suffered in 2015; to the contrary, the SPÖ won an absolute majority, while the ÖVP failed to gain any seats.