1Place olive oil and vinegar in bowl or casserole dish. wire whisk until blended. Add remaining spices. Blend. Place chicken breast in marinade and cover. put in refrigerator for several hours or overnight [for best flavor]
2Remove about a cup of marinade from dish before grilling and set aside. You will use 1/2 of this for onions and 1/2 for chicken.
Slice up 4 onions into quarters then slices DO NOT dice and place in frying pan with 1/2 cup of marinade mixture. cook until tender and almost clear and brown.
3Place chicken on grill and drizzle by tablespoons 1/2 of the marinade mixture. Grill until firm and cooked thoroughly. take off grill and carefully slice lengthwise into strips and serve warm with tortillas, onions, lettace, salsa and whatever else you like with your fajitas