1. Combine 2 tablespoons juice, 2 teaspoons garlic, 1 teaspoon oregano, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a bowl. Add 1 tablespoon oil, stirring with a whisk. Add chicken, and stir; marinate in refrigerator 2 hours, covered.
2. Remove chicken from bowl; discard marinade. Thread chicken onto 4 (10-inch) skewers. Heat a grill pan over high heat. Add skewers; cook 6 minutes or until done, turning often.
3. Combine remaining 1 tablespoon juice, 1 teaspoon garlic, 1/2 teaspoon oregano, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a medium bowl. Gradually add remaining 2 tablespoons oil, stirring well with a whisk. Add parsley and tomatoes; toss to coat. Serve chicken on top of salad.