Mary Kate and Ashley: Winner's Circle is an isometric horse racing game. You pick either one of the Olsens, and a horse, then an event. Most events are essentially clock or checkpoint race where you must make it through the track or jump all the gates before time runs out, but there are also challenge stages with more varied goals such as collection.
Gameplay involves controlling your chosen Olsen and horse, using either left and right to turn the horse or a directional pad to point in the direction. You can use B to kick the horse into action and A to signal them to jump. The controls allow for two different play styles, adding variety to the racing experience.