Preheat oven to 375 degrees F.
Slice peaches into a medium size bowl. Stir in sugar. Set aside for about 30 minutes to allow the sugar to pull some of the juice out of them.
In a separate bowl, mix Cinnamon Oatmeal Cookie Mix with softened butter by using a pastry blender, or a fork.
Drain the peaches, reserving 1/4 cup of peach juice, and put into a separate bowl. Stir in the flour, lemon juice, vanilla, and salt. Pour peach juice mixture over peaches and stir. Put peach mixture into a 9x13'' pan. Sprinkle cinnamon oatmeal topping evenly over peaches. Bake for 30-35 minutes or until golden brown and top is set. Remove from oven and allow to cool for at least 10 minutes before serving. Serve with vanilla ice cream, if desired.