In a bowl, mix the olive oil, red wine vinegar, Dijon mustard, garlic powder, salt, and pepper. Spread the green bell pepper, yellow bell pepper, mushrooms, and onion on a baking sheet. Pour the oil and vinegar mixture over the vegetables.
Broil the vegetables 5 minutes, stirring occasionally, until lightly scorched. Remove from heat, and cool.
Bring a large pot of lightly salted water to a boil. Add penne pasta, cook for 8 to 10 minutes, until al dente. Drain, and rinse with cold water to cool.
In a large bowl, toss the vegetables, pasta, and mayonnaise. Top with Parmesan cheese to serve.