Soon after moving to Ohio from Wisconsin, Osthaus came into national prominence as a painter of bird hunting dogs (setters and pointers). As time went on, he created more and more paintings of bird hunting dogs, painting the winners of the National Field Trial Championships from 1896 through 1910. The series included some of the most famous bird hunting dogs in the nation's history. Osthaus painted from nature, making many sketches of the background. He would pose dogs for long periods of time, capturing their natures and characteristic expressions.