Cook onions and stir 2-3 min. or until soft. Add garlic, stir 1 min. Add broccoli and carrots, stir 2-3 min. Add bell pepper and cook another 2 min. Add the squash/zucchini, tomatoes, and mushrooms, stirring 2-3 min or just until all veggies are soft.
Add Italian seasoning, salt, and pepper to the veggie mixture, stirring to combine well. Dissolve cornstarch in broth; when fully dissolved, add to the veggie mixture and bring to a boil until thickened.