If you’re using a slow cooker, first cook the vegetables on the stovetop or in the microwave. To microwave, combine all of the ingredients, including the olive oil, onion, celery, peppers, garlic, cumin and oregano in a large heatproof bowl, and season with salt and pepper. Microwave on high, stirring occasionally, until the vegetables are tender, about 6-8 minutes. Otherwise, heat the olive oil in a 12-inch skillet or large pot (use a pot if you're cooking the soup on the stovetop) over medium-high heat. Add the onion, celery and peppers. Season with salt and pepper. Cook, stirring occasionally, until the vegetables are softened, about 5 minutes. Add the garlic, cumin and oregano, and stir until fragrant, about 30 seconds. At this point you can either finish cooking the soup on the stovetop or in a slow cooker.