Preheat oven to 400 degrees F.

Spray an oven-safe skillet with non-stick cooking spray and heat over medium-high heat.

Add olive oil to pan, and when hot, saute onion.

When onion begins to brown, add spinach and continue to cook until spinach is wilted; remove from heat and cool.

In a large bowl, whisk eggs, salt, pepper, parmesn and romano cheeses.

Pour eggs over vegetables in skillet and top with bite-sized pieces of fresh mozzarella cheese.

Cook in oven for 25 minutes, or until eggs are set.