Combine 1 cup 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. Loosely cover with a tea towel and let dough rest for 10 minutes.
Pat dough with floured hands to fill greased pizza pan or baking sheet. OR roll dough on a floured counter to 12-inch circle; place in greased pizza pan or baking sheet. Form a rim by pinching the edge of the dough.
Spread with ranch dressing, leaving about an inch of crust all the way around. Top with chicken, red onion, and bacon and sprinkle with cheese.
Bake on the lowest oven rack for 12 to 15 minutes, until cheese is bubbly and crust is browned.