Preheat skillet to medium–high heat. Add vegetables, green peppers, red peppers, yellow peppers, and white onion. Sauté vegetables and remove from heat.
Cook for 4 minutes covered, flip, and continue to cook for 3 additional minutes, covered, or until internal temperature of 145°F is reached on instant read thermometer.
Remove from heat, let rest for 3 minutes.
After 3 minutes of rest, cut beef into 1–inch thick strips, and add beef back into skillet with sauteed vegetables.
(This dish can stay plated in skillet, but we can have the tortillas, sour cream, and salsa to a side)