Wash and slice all of the vegetables. To peel the tomatoes drop them in boiling water for about 10 seconds and use a sharp paring knife to help slip off the peel.
Heat 2 tablespoons olive oil in a skillet on medium heat. Add the sliced eggplant and cook, turning occasionally for five minutes. Sprinkle with salt and pepper and remove the eggplant from the skillet.
Add 1 tablespoon olive oil to the skillet and add the zucchini slices. Cook for about five minutes, turning occasionally, then season with salt and pepper and remove from the skillet.
Repeat the procedure for the bell peppers.
Heat 2 more tablespoons olive oil in a Dutch oven on medium heat and add the onions. Cook, stirring occasionally, for five minutes.
Add the tomatoes and the pre-cooked vegetables: eggplant, zucchini, and bell peppers. Stir to combine and then add the bay leaf and thyme. Cover and cook on low heat for 30 minutes.
Add the garlic and salt and pepper if needed and cook covered for another 10 minutes.