Preheat oven to 350. Grease a 9X13 baking dish.

In large skillet, heat oil and add mushrooms, onions, red pepper, spinach, and seasonings. Cook until the vegetables are soft then drain them on a paper towel lined colander. 

Whisk eggs in a large bowl.

Stir eggs in spinach mixture and add about 3/4 of cheese.

Pour the mixture into the prepared pan, scatter remaining cheese on top and bake 25 to 30 minutes or until lightly browned.

Cool for 10 minutes, cut into squares and serve. Serves 4 to 6 depending on how small or large you cut it.