Preheat oven to 350 degrees F.

Lightly grease a 13-by-9-inch baking dish.

Combine vegetables, cream cheese, chopped onion, salt and pepper in a large saucepan over medium heat. Cover and cook 20 minutes, stirring occasionally, until cheese and cream cheese are melted. Pour into prepared baking dish.

Unroll seamless dough sheet and lay over vegetable mixture, tucking in the edges if necessary.

Bake 25 minutes until golden brown. Cool 15 minutes before serving.