Van Os was particularly fond of animals as his subject matter and made such an excellent copy of one of Potter's works - Young Bull - that it was purchased by William V, Prince of Orange.

After completing his training, he departed for Amsterdam, where he supported himself primarily by painting rather mediocre portrait miniatures and giving drawing lessons.

Around 1805 he began to devote himself to producing landscape paintings filled with his favourite subject of cattle and was still strongly influenced by the 17th-century Dutch masters.

Emperor Alexander I of Russia purchased a picture in this theme by Van Os and placed it in his palace at St. Petersburg.

His son Pieter Frederik van Os (1808–1892) became a painter and teacher who taught Anton Mauve among others.