Pre-heat the oven to 400 degrees. Grease the bottom of a medium casserole dish. In a large skillet,fry bacon until crisp.
Cook noodles according to package directions. While noodles are cooking, in a saucepan over medium heat melt the butter. Mix in the flour, onion salt, and pepper until smooth. Slowly whisk in the milk. Add cheese until the sauce becomes thick.
Drain noodles, stir them into the cheese sauce in a bowl. Add bacon. Pour the mixture into the casserole dish. Combine bread crumbs and melted butter in a bowl. Sprinkle the bread crumbs mixture over the noodles in the casserole dish.