HEAT oven to 350ºF.
CHOP 6 oz. chocolate. Combine flour and baking powder. Beat butter and sugars in large bowl with mixer until light and fluffy. Add eggs, orange zest and 3 Tbsp. orange juice; mix well. Gradually add flour, mixing well after each addition. Stir in chopped chocolate and cranberries.
POUR into greased and floured 12-cup fluted tube pan or 10-inch tube pan.
BAKE 1 hour to 1 hour 10 min. or until toothpick inserted near center comes out clean. Cool in pan 10 min. Remove from pan to wire rack; cool completely.
HEAT remaining chocolate and orange juice in saucepan on low heat until chocolate is completely melted and mixture is well blended, stirring frequently. Drizzle over cake; let stand until firm.