Pre-Heat oven to 375 degrees
Using a sharp knife or pizza cutter, cut one pie crust into strips. Put the other Pie crust into your pie dish forming it to the pan and bringing the edges up over the pie pan.
In a large Mixing bowl, add Blueberries, blackberries, and peaches. Fold in sugar, corn starch, and cinnamon.
In a small bowl add cornstarch and cold water sir until there are no lumps add to fruit mixture and stir well. Pour ingredients into pie shell then top with small cut pieces of butter. Then lay strips onto pie in a lattice style. Put the pie into the oven. Fr 15 minutes bake at 375 then turn down to 350 degrees and bake for another 45 minutes.