1. Pour oil into a large saucepan and add onion. Sauté over medium flame for about three minutes. Add garlic and sauté for an additional one minute. Add zucchini and salt and pepper to taste. Cover and cook on low for 10 minutes.
2. Add marinara sauce; mix, cover and cook an additional 25 minutes. Squash should be soft.
3. Serve over rice.