Preheat oven to 375°F. Spray a muffin pan with cooking spray. Line each muffin cup with two wonton wrappers each. Bake for 10 minutes.
In a large skillet, heat vegetable oil over medium high heat. Cook chicken for 5 to 7 minutes or until cooked through.
Add green pepper, orange pepper, yellow pepper, onion and Fajita seasoning mix and stir to combine. Cook for an additional 5 minutes or until veggies are slightly softened.
Add 1 to 2 tsp of fajita mixture to wonton cups. Top with sour cream, shredded cheese and green onions, if desired.