Heat oil in a large saucepan over medium heat. Add onion, green pepper, and garlic. Cook, stirring frequently, until tender. Add small amounts of water, a few tablespoons at a time as necessary to prevent sticking.
Add remaining ingredients, mixing well. Bring to a boil, stirring occasionally. Cover, reduce heat to medium-low, simmer 20 minutes.
Quick tip: Keep frozen, chopped onion in your freezer! Makes meal prep so much easier/faster!