On 21 June 1852, he was appointed director of the Hessian Catholic teachers' training college at Bensheim.
During the fifteen years of his administration, encouraged by Bishop von Ketteler, Ohler laboured to infuse a better spirit into the Catholic teaching body of Hesse.
On 8 April 1867, he was made a canon of the cathedral chapter of Mainz Cathedral, given charge of educational matters, and appointed lecturer in pedagogy and catechetics at the episcopal seminary - a position he held until the seminary was closed during the Kulturkampf in 1878.
Ohler's chief work is "Lehrbuch der Erziehung und des Unterrichtes" (Mainz, 1861; 10th ed., 1884).
Ohler adapted from the Italian: "Cajetanus maria von Bergamo, Ermahnungen im Beichtstuhle" (5th ed., Mainz, 1886), "Johannes Baptista Lambruschini, Der geistliche Führer" (Mainz, 1848; 12th ed., 1872), and an abridged edition of the latter, "Der kleine geistliche Führer" (1851; 6th ed., 1861).