Coarsely grind orange in processor or blender (Rind and meat of fruit only, avoid the bitter white part of peel). Transfer to heavy medium saucepan.
Add blueberries, cranberries, 1-1/2 C sugar and cornstarch. Boil mixture over medium-high heat until thick, stirring constantly, about 3 minutes. Cool completely.
Pour filling into a 9-inch pie pan, dot filling with butter and cover with pie crust.
Crimp edges and make several slashes in top crust to allow steam to escape. Brush crust with milk. Use any remaining crust scraps to make decorations to put on top of pie. Brush with milk also. Sprinkle top of pie with sugar. Place on a rimmed cookie sheet and bake at 400 until crust is golden brown, about 50 minutes. Cool on rack 1 hour. Serve warm or room temperature.
8 Points Each;88 for Entire Recipe