Preheat oven to 400F (200C). Lightly grease a baking tray.
Cut peppers in half and remove the core. Place on the baking tray cut side down and roast for 25-30 minutes.
Meanwhile, prepare brown rice according to the directions on the package.
In a large skillet, heat grapeseed oil over medium heat.
Sauté chopped onion and garlic for 5 minutes.
Add diced zucchinis, green beans and broccoli and cook for 5 minutes over medium/high heat.
Stir in diced tomatoes and spices. Continue cooking for a couple more minutes.
Season the vegetables with salt and pepper and add the rice which should be cooked by this point. Mix well.
Spoon the rice and vegetables into the pepper halves. Return to oven to to heat up if needed for 5 minutes.