Preheat your oven to 375 degrees F. Grease a 9x9 square baking dish. Set aside.
Place the peeled, sliced peaches in a large mixing bowl. Add the brown sugar to the bowl with the peaches and toss them together.
Add the flour, lemon juice, vanilla, salt and cinnamon to the bowl and mix well. Pour the peaches into the prepared baking pan.
Make the crisp topping next. Add the flour, oats, brown sugar, baking powder and cinnamon to a large mixing bowl and stir together.
Add the cold butter to the bowl and blend together. I like to use my hands to rub the butter into the flour and oat mix. Mix in the butter until it is in small crumbles. Sprinkle the oat mix over the peaches in the baking pan.
Bake the crisp for 35 minutes. The top will be golden brown and the juice will be bubbling around the edges of the pan.
Let the crisp cool for about 10 minutes before scooping and serving with vanilla ice cream or whipped cream.
Notes
You can use frozen sliced peaches. Thaw the peaches first before making the filling. You will need about 3 ½ pounds of sliced peaches.