In a large skillet, cook the onion and garlic until the onion is soft. Add a bit of water if it begins to stick.
Add the bell peppers, mushrooms, oregano, basil, red pepper flakes, thyme, fennel and black olives.
Cook until the vegetables are tender-crisp.
In a medium-sized bowl, stir the crushed tomatoes, vinegar, basil, oregano, garlic powder, salt and pepper together.
Spread some sauce on each crust.
Top with cooked vegetables.
Add mild banana peppers if you like.
Cook on a baking sheet at 400° for about 10 minutes.
Top cooked pizzas with chopped greens.