Cook pasta according to package directions. Drain; keep warm.
Meanwhile, for sauce, in a medium saucepan cook carrots, zucchini, and mushrooms in margarine or butter until vegetables are tender. Stir in flour. Add milk all at once. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 1 minute more. Add beer and heat through. Remove pan from heat. Gradually add cheddar cheese, stirring just until melted. If desired, season to taste with salt and pepper.
Arrange pasta on individual plates or a large platter. Spoon the sauce over pasta. Makes 4 main-dish servings.