[header] How to cook vegetarian pasta [title] Heat the oven to 450 ° f (230 ° c). [step] It takes a while for ovens to reach this high temperature, so get it preheating while you are preparing the vegetables. [title] Mix the vegetables. 
[step] Combine the mushrooms, broccoli, spinach, pepper and onion in a large bowl. Sprinkle 1 tablespoon (15ml) of the olive oil over the vegetables and mix well to make sure everything is coated.