Beseler was a member of the Frankfurt Parliament where he participated in writing the failed 1849 German constitution. From 1849 to 1852 and from 1857 to 1887, he was a member of the Prussian House of Lords, 1850 of the Erfurt Union Parliament, and 1874 to 1877 of the Reichstag.

As a notable "Germanist" opponent of the "Romanists", led by