Preheat oven to 350 degrees. Coat a 2-quart baking dish with cooking spray.
In a large bowl, combine 2 cups nonfat milk, 2 large eggs, 1 2/3 cups sugar, 2 teaspoons vanilla extract, 1/2 teaspoon nutmeg and 1/2 teaspoon cinnamon. Beat well.
Stir in the 7 slices dry whole-grain bread, cubed and 5 cups fresh or frozen (and hawed) diced rhubarb. Pour into the prepared baking dish.
Bake, uncovered, for 60 to 75 minutes, or until a knife inserted in the middle comes out clean. Using a spatula, press down on the bread a few times during the baking process.
1. Substitute ½ cup liquid egg substitute for the 2 large eggs.
2. To reduce the calories, substitute ⅔ cup spoonable sugar replacement ⅔ cup of regular sugar (retain the remaining 1 cup regular sugar). The sugar is needed because rhubarb is very tart.