Prepare the Chicken: Filet the chicken breasts to ensure even thickness. Cut them into strips.
Marinate the Chicken: Place the chicken in a bag or bowl. Add fajita seasoning, drizzle with oil, and squeeze lime juice over the chicken. Marinate for at least 20 minutes or overnight.
Grill the Chicken: Preheat the grill to medium-high heat. Grill the chicken for about 20 minutes, flipping halfway through.
Grill the Vegetables: Cut the bell peppers into quarters and the onion into thick slices. Grill alongside the chicken for about 5 minutes or until tender.
Warm Tortillas: Place tortillas on the grill for a few seconds on each side to warm them.
Assemble and Serve: Slice the grilled chicken and vegetables. Serve with warm tortillas and your choice of toppings.