Slice chicken breasts into strips, about an inch apart, and coat with chili powder, cumin, garlic powder, salt, and pepper.
In a large skillet, heat 1 tbsp vegetable oil and add chicken. Avoid moving the chicken too much at first to develop a slight char. Once chicken is no longer pink, remove from the skillet and set aside.
Heat more oil, then add onion. Cook until the onion is slightly translucent. Add garlic, peppers, and cook until the peppers are crisp tender. Return chicken to pan, mix, then remove from heat.
Serve immediately with garnish of your choice on a tortilla, or divide into 4 food storage containers and store in the refrigerator. Can be kept refrigerated for up to 4 days.