Cut corned beef into 1/2-inch strips; set aside.
Saute cabbage and next 3 ingredients in a large nonstick skillet coated with cooking spray 4 minutes or until cabbage wilts. Remove from heat; stir in dressing. Cool.
Stir together butter and mustard; set aside.
Unfold phyllo, and cover with a damp towel to prevent pastry from drying out.
Stack 8 sheets on a flat surface covered with wax paper, brushing every other sheet with the butter mixture. Spoon half of the cabbage mixture lengthwise down half of phyllo stack, spreading to within 2 inches of edges. Top with half of corned beef and half of cheese. Fold in short edges 2 inches.
Roll up, staring a long edge nearest filling. Place, seam side down, on a baking sheet coated with cooking spray. Cut 1/4-inch deep diagonal slit, 1 inch apart, across top. Coat strudel with cooking spray. Repeat with remaining phyllo, butter mixture, and filling.
Bake at 425 degrees Fahrenheit for 12 to 15 minutes or until golden. Cut diagonally into 3- to 4-inch pieces. Serve immediately.