Place chicken in a resealable plastic bag. Add yogurt, oil, lemon juice, paprika, cumin oregano, salt and garlic, and massage the mixture into chicken to cover completely. Marinate chicken in refrigerator for at least 3 hours.

Preheat grill to medium-high heat. Add chicken to the grill and cook 6-8 minutes per side, or until the chicken reaches an internal temperature of 165°F. Let rest for 5 minutes before slicing.

Cut the Tribeca Oven French Baguette in half horizontally.

To build the sandwich, spread tzatziki sauce evenly over both the bottom half and top half of the bread. Top bottom half with an even layer of chicken, tomatoes, cucumber, lettuce, onion and then the remaining top half of bread, sauce-side-down. Cut into 4 sandwiches and serve.