In a large nonstick skillet cook grapes over medium heat for 2 to 4 minutes or just until grapes are softened. Drain off any liquid.
Layer four of the bread slices with ham, grapes, and cheese. Top with the remaining four bread slices. Lightly spread the outsides of sandwiches with butter or brush with olive oil.
Rinse and dry the skillet. Preheat skillet over medium heat. Place sandwiches, half at a time if necessary, in skillet. Cook for 2 to 3 minutes or until bread is toasted. Turn sandwiches and cook for 1 to 2 minutes more or until bread is toasted and filling is heated through. Serve immediately.