Preheat oven to 375°
Put butter in a 13 x 9 inch baking dish and melt in the oven.
In a bowl, combine flour, sugar, baking powder, and salt.
Add milk, stirring just until dry ingredients are moistened.
Pour batter over melted butter, do not stir.
Add in the peach slices (do not include the syrup, if you think using the whole jar is too much, add less and use the remaining peaches for your pancakes next time).
Bake for 40 to 45 minutes or until golden brown.
Serve warm with a scoop of vanilla ice cream or sweetened whipped cream.