Barnard began her public career as an officer of the Provident Association, an Oklahoma benevolent organization. She soon became interested in such social legislation as compulsory education and the abolition of child labour. Those concerns led her to actively lobby for progressive issues at the Oklahoma constitutional convention in 1906. She was elected in 1907 to the state office of commissioner of charities and corrections, leading the state Democratic ticket while becoming the first woman in the world to hold such a post.

While state commissioner from 1907 to 1914, Barnard won national attention for her promotion of reform legislation on such issues as child labour, prison reform, Indian rights, and the improved care of the insane.