Combine the oil and fajita seasoning in a small bowl. Once well mixed, pour half of the sauce over the steak, toss and coat in a bowl and set aside to marinate.
In a separate bowl, pour the other half of the fajita sauce over the sliced peppers and onions until well coated.
Heat a large skillet on medium high and add the peppers and onions. Saute until translucent, about 7-10 minutes. Remove from skillet.
Saute steak in skillet to desired doneness, 3-5 minutes.
Mix the peppers and onions with the steak in the skillet and serve hot with tortillas and toppings of choice. Enjoy!