FILLING: Pour pineapple into saucepan; boil rapidly for 10 minutes to reduce syrup. Blend sugar, cornstarch and salt well; stir into hot pineapple. Cook, stirring constantly until clear and thickened. Remove from heat, stir in butter and orange peel; cool.
Prepare Oat Crumbles; spoon HALF into a 9 x 13 x 2 inch pan; pack down firmly. Cover evenly with pineapple mixture. Sprinkle remaining Oat Crumbles over top; press down lightly. Bake in a preheated 375°F oven 20 to 25 minutes until lightly browned. Cool before cutting. Makes about 2 1/2 dozens bars 1 1/2 x 2 inches.
OAT CRUMBLES: Sift 2 cups all purpose flour with 1 teaspoon baking powder and 1/2 teaspoon salt. Add 1 1/2 cups brown sugar (firmly packed), 2 cups uncooked quick cooking oats, and 1 cup butter; blend until crumbly.