Heat olive oil in a large Dutch Oven, or large heavy-bottomed pan, over medium heat. When oil is shimmering but not smoking, add garlic and allow it to cook until fragrant, about one minute.
Add onions and carrots and allow them to cook, stirring occasionally until they begin to soften, about 5-6 minutes. If you are including bay leaf, add it now. Salt and pepper lightly.
Add zucchini and squash, salt and pepper this layer lightly, and allow to cook with carrots and onions, stirring to combine then occasionally and gently to prevent burning on the bottom, until they also begin to soften, about 3-4 minutes.
Add mushroom, tomatoes, and any herbs you plan to include, salt and pepper this layer lightly, and allow to cook for an additional 10 minutes, stirring occasionally and gently to combine and prevent burning on the bottom.
Remove bay leaves. Transfer into a serving dish and top with fresh parsley. Enjoy!