Halve the grape, pear, and/or cherry tomatoes or cut small yellow tomatoes into wedges; set aside. Place a large skillet on grill side burner. In skillet, heat oil over medium heat for 2 minutes. Add onion, garlic, and thyme; cook and stir for 2 to 3 minutes or until onion is tender.
Add tomatoes, salt, and pepper. Cook and stir for 1 to 2 minutes or until tomatoes are just warmed. Remove from heat. Stir in mozzarella cheese. Makes 4 servings.