Using a sharp knife, completely remove the outer skin and white pith of the grapefruit. Hold the grapefruit over a bowl, and cut out the sections, letting them fall into the bowl. Cut the orange sections into a separate bowl.
On each of 8 (8-inch) dessert plates, arrange 6 grapefruit sections and 6 orange sections in an alternating pattern around plate.
Spoon 1/4 cup yogurt onto the center of each grapefruit-orange arrangement, and sprinkle each with 1/2 tablespoon granola. Serve.