Warm the olive oil over medium heat in a small saucepan. Add the rosemary leaves and remove from the heat. Let cool.

In a large bowl, sprinkle the yeast over the warm water. Let stand until the yeast is foamy - about 5 minutes. Stir until dissolved.

Add the olive oil and rosemary, 3 cups of the flour, 2 Tablespoons of the sugar, and the salt to the yeast mixture, and stir until a soft dough forms.

Turn the dough out onto a floured work surface and knead until smooth and elastic - about 10 minutes. Add more flour if the dough feels sticky. Oil a large bowl and place the dough in it, turning it around to make sure all sides of it get oiled. Cover with a towel and let rise in a warm place until doubled in bulk - about 45 minutes.

Preheat the oven to 375° F. Flour a 15 x 10 x 1-inch jelly roll pan.

Punch the dough down to eliminate air bubbles. Stretch the dough out with your hands to fit the prepared pan. Scatter the grapes and nuts evenly over the dough, pressing them in lightly. Sprinkle the remaining 2 Tablespoons of sugar over the dough. Bake for 30-35 minutes, or until the dough is lightly browned and crisp.

Slide the focaccia out of the pan and onto a rack. Serve warm or at room temperature.