Except of 1908, when the family moved temporarily to Cape Cod, Massachusetts, where his father worked with Alphonse Mucha.
[1] He spent the following year in Paris, studying at the École des Beaux Arts and with Pierre Laurens and Frank Kupka, and returned to California in 1928.
[1] Early in his career, Kosa Jr. worked as a mural painter and designer for various architects and interior decoration firms.
[1] He painted mainly California landscapes and urban settings in both oil and watercolor, and he also produced commissioned portraits of celebrities, businessmen, and politicians.
[1] His work was widely exhibited starting in the 1930s, with solo shows at the Los Angeles County Museum of Art and elsewhere.