Roll out half of pastry 3/8 inch thick, line 9 inch pie plate. Combine rhubarb and strawberries. Combine sugar, tapioca, orange peel and salt; sift over fruit and combine lightly. Roll out remaining pastry and cut in strips. Turn filling into pastry-lined pie plate. Dot with butter. Weave pastry strips on top. Crimp edges of crust. Fold strip of foil over crust.
Bake in preheated 400 degree oven for 40 to 50 minutes OR start in 450 degree for 10 minutes and then turn down to 350 degrees for 30 minutes longer. Crust is less likely to burn with the second method. Pie should bubble and have golden crust. Serve slightly warm.
