Preheat the oven 350 degrees F. Combine all ingredients, except the tomatoes, in a bowl. Cut the tops off the stem ends of the tomato. Carefully scoop out the flesh to create a cup to stuff the vegetables in. Place the tomato cups in a parchment-lined or non-stick baking dish. Fill them with the vegetables. Cover and bake 20 minutes, or until the vegetables are just heated through.
Recipe Options: Stuff the tomatoes with a single frozen vegetable, such as peas or cut green beans, rather than a mix of vegetables. Use yellow "on the vine" tomatoes instead of red. Use a different herb, such as chopped oregano, parsley or basil, to flavour the vegetables instead of sage.