Oswald Heer was educated as a clergyman at Halle and took holy orders, and he also graduated as Doctor of Philosophy and medicine.

Early in life his interest was aroused in entomology, on which subject he acquired special knowledge, and later he took up the study of plants and became one of the pioneers in paleobotany, distinguished for his researches on the Miocene flora.

[1] In 1837, Carl Daniel Friedrich Meissner (1800–1874) a Swiss botanist named a genus of flowering plants (in the family of Anacardiaceae) from South Africa after him, Heeria.

Heer published a critique of Darwinism in volume 2 of his 1867 book The Primaeval World of Switzerland, concluding "All these facts afford arguments against a slow and uniformly progressive transformation of species, and lead to the conclusion that the transformation of organic nature took place in a period of comparatively limited duration" (p. 288).

During a great part of his career Heer was hampered by slender means and ill-health, but his services to science were acknowledged in 1874 when the Geological Society of London awarded to him the Wollaston medal.