Preheat oven to 425°F.
Combine 2 cups flour, undissolved yeast, sugar and salt in a large bowl. Add very warm water and oil; mix until well blended, about 1 minute.
Gradually add enough remaining flour to make a soft dough.
Dough should form a ball and will be slightly sticky. Knead** on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes. (If using RapidRise Yeast, let dough rest at this point for 10 minutes.) Divide dough in half.
Bake for 18 to 20 minutes, until cheese is bubbly and crust is browned. For best results, rotate pizzas between top and bottom oven racks halfway through baking.
*If you don't have a thermometer, water should feel very warm to the touch.
**To knead the dough, add just enough flour to the dough and your hands to keep the dough from sticking. Flatten dough and fold it toward you.Using the heels of your hands, push the dough away with a rolling motion. Rotate dough a quarter turn and repeat the "fold, push and turn" steps. Keep kneading dough until it is smooth and elastic. Use a little more flour if dough becomes too sticky, always working the flour into the ball of dough.