Preheat BBQ or preheat oven to 375 F / 190 C.
Brake off the bottoms of the asparagus. Cut the onion, bell pepper in big cubes. Slice the mushrooms. Put into aluminum tray and add salt and pepper to taste. Give a splash of olive oil. Put on BBQ for approximately 20 to 30 minutes, cover with foil. 10 minutes before time give it a splash of red wine vinegar.
If using the oven, bake for approximately 35 to 45 minutes. Cover with foil and give it 10 minutes before time a splash of red wine vinegar. It will give it a savory taste!