Add the red and brown rice to a saucepan with 6 cups (1.5 liters)of water and a big pinch of salt. Cover with a lid and bring to aboil over a medium-high heat, then reduce the heat to a simmer and leave to cook for 15–20 minutes, until the grains are soft and all the water has been absorbed (if there is any water left at this point, simply drain it away). If you prefer, you can cook this in a rice cooker instead.
Combine the quinoa and bulgur wheat and cook them in 2 cups (500 ml) of salted water until soft, draining off any remaining water as before. Leave the mixture to sit in the hot saucepan for 5–10 minutes to dry out and fluff up.
Heat the olive oil in a small frying pan over a high heat, add the beans, and fry with a pinch of salt for 4–5 minutes until tender and starting to brown. Leave to cool.
To make the lemon-parsley oil, add the garlic and 1 teaspoon of salt to a mortar and pound together with a pestle to form a rough paste. Add the parsley and pound until the leaves are broken down and the paste is green, then stir in the oils and lemon juice, and season to taste with salt and pepper.
Combine the red rice, brown rice, quinoa, bulgur wheat, chickpeas, green beans, green olives, green onion, and parsley in a big bowl and stir well, then season with salt and pepper. To serve, scatter over the walnuts and drizzle over the lemon-parsley oil.