Heat oven to 425 degrees F. In a medium saucepan cook the pasta according to package directions. Add broccoli, carrots, or beans during last 3 minutes of cooking. Drain pasta mixture. Return to pan; keep warm.
Meanwhile, in large saucepan cook onion in 2 tsp. of the oil over medium heat for 5 minutes or until tender, stirring occasionally. Remove pan from heat. Add semisoft cheese; stir until cheese is melted and combined.
In a medium bowl whisk together milk and flour until smooth. Add all at once to onion mixture. Cook and stir over medium heat until thickened and bubbly. Reduce heat to low. Stir in cheddar and Asiago cheeses until cheeses are melted. Add cooked pasta mixture; stir to coat.
Transfer pasta mixture to 2-quart casserole. In small bowl combine baguette crumbles and remaining 2 tsp. oil; sprinkle on pasta mixture. Bake, uncovered, 10 to 15 minutes or until top is browned. Sprinkle with parsley. Makes 6 servings.