Combine first 9 ingredients in a large zip-top plastic bag. Seal and marinate in refrigerator 1 hour. Remove steak from bag; discard marinade.
Sprinkle bell peppers and onion with salt and pepper.
Heat a large grill pan coated with cooking spray over medium-high heat. Add the bell peppers, and cook for 5 minutes. Turn the bell peppers over, and add the onion. Cook for 5 minutes, turning the onion once. Remove the bell peppers and onion, and keep warm. Add the steak, and cook for 5 minutes on each side or until desired degree of doneness. Cut steak diagonally across the grain into thin slices.
Warm tortillas according to package directions. Arrange about 3 ounces steak, 2 bell pepper wedges, and 1 slice onion down center of a tortilla. Fold sides of tortilla over filling. Repeat the procedure with the remaining tortillas, steak, pepper wedges, and onion slices.