Heat olive oil in a large skillet over medium-high heat.
Season the chicken strips with chili powder, cumin, garlic powder, onion powder, smoked paprika, salt, and pepper.
Add the seasoned chicken to the hot skillet and cook for about 5-7 minutes, stirring occasionally until the chicken is browned and cooked through.
Remove the chicken from the skillet and set aside on a plate.
In the same skillet, add the sliced bell pepper and onion. Sauté for about 3-4 minutes until they are tender-crisp.
Return the cooked chicken to the skillet with the veggies and toss everything together to heat through, about 1-2 minutes.
Serve the chicken and vegetable mixture in warmed tortillas and top with your choice of optional toppings.