Kass painted her first Oy painting in 2009, and her first Yo in 2010. The two paintings are covers of a painting by Ed Ruscha from 1962 called Oof, currently in the collection of MoMA. For her paintings, Kass appropriated the same hues and font that Ruscha used in his. In 2015, Two Tree Management Art in the Dumbo neighborhood of Brooklyn commissioned Kass to create a monumental public sculpture version of OY/YO for the Brooklyn Bridge Park. Standing approximately 96 x 196 inches, the aluminum sculpture spells "YO" when viewers look at is towards Brooklyn, and "OY" when viewers look at it towards Manhattan. Kass has also created other manifestations of this ongoing series.