Step 1) Combine marinade mix, water and oil in a resealable plastic bag; blend well.
Step 2) Add chicken and vegetables to marinade in bag; turning to coat. Marinate 15 minutes, turning occasionally.
Step 3) Remove chicken and vegetables from bag; discard remaining marinade.
Step 4) Place vegetables on a grill pan over Direct Medium heat and grill 3 to 5 minutes or until crisp tender. Grill chicken for 12 to 16 minutes, turning once, until cooked through. Remove from heat and let rest 5 minutes.
Step 5) Slice chicken into strips. Serve on tortillas with grilled vegetables. Top with guacamole, sour cream, salsa and shredded cheese, if desired.