In a large saucepan or Dutch oven, cook onion in butter or margarine until tender.
Carefully add water, bouillon granules, garlic, and black pepper to the onion mixture. Bring to boiling.
Thoroughly rinse the wild rice. Add to boiling mixture with brown rice. Return to boiling; reduce heat. Cover and simmer for 25 minutes.
Stir the long-grain rice into the mixture. Return to boiling; reduce heat. Cover and simmer for 15 minutes more or until the rice is tender.
Stir in red or green sweet pepper and chives. Makes 8 side-dish servings.