Preheat oven to 375 degrees F. In medium bowl, with wire whisk or fork, mix eggs, milk, salt, and pepper. Stir in diced tomato and chopped chives. In nonstick 10-inch skillet with oven-safe handle (or wrap handle with heavy-duty foil), melt margarine or butter over medium heat. Pour in egg mixture; drop spoonfuls of goat cheese on top of egg mixture. Cook 3 to 4 minutes until frittata begins to set around the edge. Place skillet in oven. Bake 9 to 10 minutes or until frittata begins to set and knife inserted in center comes out clean.