Preheat oven to 400°.
Combine first 4 ingredients in a medium bowl. Combine vanilla and egg whites in a small bowl; stir with a whisk until foamy. Add egg mixture to oat mixture, stirring until well blended.
Spoon about 1 tablespoon oat mixture into each peach half. Arrange peach halves on a baking sheet. Bake at 400° 13 minutes or until oat mixture is set. Serve with frozen yogurt.