Heat 1 tablespoon of oil in a 23cm heavy-based frying pan on medium. Add zucchini, onion and capsicum. Season to taste and cook for 10 minutes, stirring, until tender. Cool slightly.
Whisk together eggs, parsley and half of parmesan. Add vegetables and stir to combine. Wipe pan and heat remaining oil on medium. Pour in egg mixture, distributing vegetables evenly. Cook frittata for 7 minutes, without stirring, until edge is set but centre is still soft.
Remove from heat, sprinkle with remaining parmesan. Place under a preheated grill and cook for 3 minutes, until golden. Slide frittata onto a serving plate and cut into wedges. Serve with bread.