HEAT oil in medium skillet on medium-high heat. Chop pepper and onions; cut wieners into 1/2-inch-thick slices. Add vegetables and wieners to skillet; cook 2 min. or until peppers are crisp-tender. Stir in tostadas; cook 1 min. or until slightly softened, stirring occasionally.
WHISK eggs until well blended.
ADD to skillet; cook 3 min. or until almost set, stirring occasionally. Top with cheese; cover. Cook 1 min. or until melted.