Heat oven to 450°F. Prepare pie crust as directed on package for one-crust baked shell. Place crust on ungreased cookie sheet.
Invert 2-quart casserole over crust. With sharp knife, trace and cut around casserole rim; remove casserole. Trim an additional 1/4 inch from edge of casserole-shaped crust. Using small cookie cutter or sharp knife, cut holes in crust. Cut additional shapes out of dough scraps, if desired; arrange over crust. Bake at 450°F. for 9 to 11 minutes or until light golden brown.
Meanwhile, melt margarine in large saucepan. Stir in flour, marjoram and pepper; cook until mixture is smooth and bubbly, stirring occasionally. Gradually stir in milk and broth; cook until mixture boils and thickens, stirring constantly.
Add chicken and vegetables. Cook 10 to 15 minutes or until vegetables are tender, stirring occasionally. Spoon mixture into casserole; place baked crust on top.