Stir until cheese is completely melted. Spray 8-inch square pan with cooking spray. Spoon grits mixture into prepared pan.
Press grits evenly into pan with wet fingertips.
Refrigerate until cold. Turn polenta out onto cutting board and cut into 2-inch squares. Cut each square diagonally into 2 triangles. Spray baking sheet with cooking spray. Place polenta triangles on prepared baking sheet and spray tops lightly with cooking spray.