Combine the crust ingredients; press onto the bottom and up the sides of a greased 9-in. pie plate; set aside.
In a saucepan, cook broccoli, cauliflower, carrots and onion in a small amount of water until crisp-tender; drain well. In another saucepan, combine mayonnaise and flour until smooth; cook and stir until bubbly. Gradually add milk, salt and pepper; cook and stir over medium heat until thick, about 3 minutes. Stir in vegetables; pour into the crust.
Sprinkle with cheese.
Bake, uncovered, at 350° for 30-40 minutes or until crust edges begin to brown.