Combine yogurt, garlic, 2 Tbsp. oregano, 1 Tbsp. parsley, lemon juice, and pepper in a medium bowl; whisk to blend.

Place chicken in a glass dish. Top with yogurt mixture. Marinate in the refrigerator, covered, turning once, for at least 1 hour and up to overnight.

Preheat grill or broiler on high.

Combine cheese, tomato, artichoke hearts, sun-dried tomatoes, remaining 1 Tbsp. oregano, and 1 remaining Tbsp. parsley in a large bowl; mix well. Set aside.

Grill or broil chicken for 4 to 5 minutes on each side, or until no longer pink in the middle. Set aside.

Heat oven 350° F.

Place chicken on a baking pan lightly coated with spray. Top each piece with 1 rounded Tbsp. of cheese mixture.

Bake for 5 to 8 minutes, or until the cheese is lightly browned.