Preheat oven to 350 degrees F.
Peel and slice peaches. Place in a bowl and stir in ⅓ cup sugar. Let sit for 30 minutes, stirring occasionally.
Using a strainer, drain the peaches and reserve ¼ cup of the “juice”.
Mix the cornstarch, 1 tsp flour, lemon juice, and vanilla with the peach juice and add to peaches. Stir to combine.
Place peaches into the bottom of a baking dish (I used an 8x8 square dish).
Combine oats, brown sugar, cinnamon and flour and sprinkle over top of peaches.
Take small bits of softened butter and place dabs on top of the topping, being sure to evenly distribute the butter.
Bake At 350 for 30-35 minutes. Topping will be slightly browned and peaches will be bubbling.