To “blind bake” pie crusts, place parchment paper in the bottom of pie crusts. Place pie weights or dried beans on top of paper. Place in oven and bake 10 to 15 minutes, until firm. Remove from oven; remove weights and paper. Return crusts to oven and bake 5 minutes longer, until light golden. Let cool 5 minutes before adding filling.
Combine all topping ingredients in a small bowl; mix with a fork until crumbly. Set aside.
Combine all filling ingredients in a large bowl. Whisk well. Pour into pie crusts.
Bake pies 15 minutes. Reduce oven temperature to 350F and continue baking 30 minutes. Remove from oven and sprinkle on topping. Return to oven and bake 15 minutes or until a knife inserted into the center comes out clean. If fluted edges of crusts begin to brown too much, place foil rings or metal pie crust shields over edges during last 15 minutes of baking.