Mix kidney beans, wax beans, green beans, garbanzo beans, corn, mushrooms, onion, green bell pepper, cider vinegar, 1/2 cup sugar, vegetable oil, black pepper, salt, basil, and oregano in a large bowl.
Chill in refrigerator for 8 hours or overnight.
Stir 1/4 cup sugar into the bean salad. Taste and add more if needed to balance vinegar flavor.