Preheat oven to 350°. Prepare brownie batter according to package directions for fudge-like brownies. Spread on a greased 12-in. pizza pan to within 1 in. of edges.
Bake 20-25 minutes or until a toothpick inserted in center comes out clean. Cool completely in pan on a wire rack.
Tint frosting orange; frost brownie. For stem, arrange green M&M's in a square pattern at top of pumpkin. For each eye, arrange 10 brown M&M's in a triangle. For nose, arrange six brown M&M's in a triangle. Arrange remaining M&M's for a mouth. Yield: 16 servings.