1. Cook sirloin steak strips in 1 tsp oil in a large skillet on medium-high heat for 3 minutes. Add red peppers, green peppers and onion; cook 3-4 minutes.
2. Add marinade, salsa; reduce heat to medium-low. Cook unitl heated.
3. Fill warmed tortillas with meat and veggie mixture. Serve with a spoonful of guacamole and/or sour cream if desired.