Mix vinegar, 2 tablespoons of the oil, chili powder, garlic powder, oregano and cumin in medium bowl until well blended. Reserve 2 tablespoons of the marinade for corn salsa. Place steak in large resealable plastic bag or glass dish. Add remaining marinade; turn to coat well. Refrigerate 30 minutes or longer for extra flavor.
Heat large nonstick skillet on medium-high heat. Add steak with marinade; cook 2 to 4 minutes per side or until desired doneness. Remove from skillet; let stand while preparing corn salsa.
Heat 1 tablespoon of the oil in same skillet on medium-high heat. Add corn, bell pepper and onion; cook and stir 8 minutes or until slightly charred. Stir in reserved marinade and cilantro. Remove from skillet. Set aside. Clean skillet.
Slice steak thinly across the grain. For each quesadilla, sprinkle 1/3 cup of the cheese over half of 1 tortilla. Layer with 1/3 cup of the corn salsa and 1/3 of the steak slices. Fold over. Heat 1 teaspoon of the remaining oil in same skillet on medium heat. Add 1 quesadilla; cook 2 to 3 minutes per side or until lightly browned and cheese is melted. Repeat with remaining quesadillas. Cut quesadillas into wedges. Serve with remaining corn salsa.