Hearty Vegetable Soup with Brown Rice

I found this recipe in a "men's health" type magazine years ago, and have (of course) adjusted it to taste. It makes a delicious and nutritious dinner, and I like to freeze the leftovers to take to work for lunch.

2 onions, diced
2 carrots, sliced
0.5 cup diced celery
2 cloves garlic, chopped
1 tablespoon olive oil
2 x 1kg tins of crushed tomatoes
1.5 cups of brown rice
1.5 cups of vegetable stock

Combine onions, celery, carrots, garlic and oil in a large saucepan, and cook for 10 minutes, stirring often. Add tomatoes to pot and bring to boil. Simmer for 10 minutes. Add rice and stock, and simmer for another 20-30 minutes, till the rice is cooked. Serves 8. You could also add some green leafy vegetables, such as kale or spinach, near the end of the cooking time.