Dutch Apple Pie with Oatmeal Streusel

I had two pie crusts and used one for pumpkin pie, so I decided to make apple pie with crumb topping to use the other crust. The recipe is from allrecipes.com
1-9 inch pie shell
5 cups apples--peeled, cored and sliced (I used closer to 6 cups)
2 T. flour
2/3 cup sugar
1/2 tsp. cinnamon
1/4 tsp. nutmeg
1/4 tsp. allspice (I did not use)
2 T. butter
Topping:
3/4 cup flour
1/2 tsp. cinnamon
1/2 cup brown sugar
3/4 cup rolled oats
1 tsp. lemon zest (I did not use)
1/2 cup butter
Preheat oven to 425 degrees. Fit pastry shell into pie pan and place in freezer.
Apple filling: Place apples in large bowl. In a separate bowl combine 2 T. flour, sugar, 1/2 tsp. cinnamon, nutmeg and allspice. Mix well, then add to apples. Toss until apples are evenly coated.
Remove pie shell from freezer. Place apple mixture in pie shell and dot with 2 T. butter. (I forgot to dot with butter, and I don't think it mattered.) Lay a sheet of aluminum foil lightly on top of filling, but do not seal (I did not cover). Bake in preheated oven for 10 minutes.
While filling is baking, make streusel topping: In a medium bowl, combine 3/4 cup flour, 1/2 tsp. cinnamon, brown sugar, oats and lemon zest. Mix thoroughly, then cut in 1/2 cup butter until mixture is crumbly. Remove filling from oven and sprinkle streusel on top.
Reduce heat to 375 degrees. Bake an additional 30 to 35 minutes, until streusel is browned and apples are tender. Cover loosely with aluminum foil to prevent excess browning. (This was not necessary in my case.)

This was good, although in places the bottom crust was a little gummy, I suspect because the apple mixture was quite juicy.