In A Large Skillet, Cook Beef And Onion Over Medium Heat Until Meat Is No Longer Pink; Drain. Stir In The Beans, Tomato Sauce, Corn, Sugar, Chili Powder And Oregano. Bring To A Boil. Reduce Heat; Simmer, Uncovered, For 10 Minutes. Sprinkle With Cheese; Remove From The Heat. Cover; Let Stand For 5 Minutes Or Until Cheese Is Melted. Serve With Tortilla Chips If Desired.