The son of an army officer, Oskar von Boenigk received a commission in the König Friedrich III Grenadier Regiment on 22 March 1912. As a platoon leader during the Battle of Longwy in October 1914, he was badly wounded in the chest. Upon recovering, he returned to his unit in the spring of 1915 and was awarded the Iron Cross, second class. Later that year, his application for a transfer to the air service was accepted and he was sent to observer school in December 1915. In March 1916 he was posted to Kampfstaffel 19. After four months he was reassigned to Kampfstaffel 32. Boenigk applied for Jastaschule in January 1917 and upon graduating he was posted to Jasta 4 on 24 June 1917. With this unit he scored five victories and was awarded the Iron Cross, first class. On 21 October 1917 he assumed command of Jasta 21. Scoring an additional sixteen victories with this unit, he was awarded the Hohenzollern House Order. On 31 August 1918 he was promoted to Oberleutnant and assumed command of Jagdgeschwader II. Stationed on the St. Mihiel Front in September, Boenigk scored five more victories, bringing his total to 26. In October he was awarded the Albert Order, second class, the Saxe-Ernestine House Order, second class, the Order of St. John and the Blue Max.
Freiherr von Boenigk served with distinction in the post-war revolution and attained the rank of Major General with the Luftwaffe during World War II. Captured by the Russians in May 1945, he died as a prisoner of war in 1946.