Which vegetables would you choose for a good breakfast to complement proteins and cereals? Why?

I would choose veggies on a protein based omelet such as onions, peppers, spinach, tomatoes, etc. I cannot think of a veg I would pair with a cereal or brain product though. Lots of fruits, but my veggie mind has gone blank.

I have always a sweet breakfast because I wake up really early in the morning, but I would something that matches with the protein: eggs with spinach, cheese and cucumber, ham and tomatoes...

I would choose tomatoes. They can be grilled or served raw and I feel that they taste great with almost all kinds of food. They also contain lycopene which has been linked to lower risk of heart disease and certain cancers!