Preheat oven to 200°C.
Place quinoa in a large saucepan or a rice cooker. Add enough water (about 4 cups) and cook it until tender.
Meanwhile, heat olive or vegetable oil in a saucepan and add onion and garlic. Sautée until slightly brown, about 2 minutes
Add mushrooms and cook over medium heat until tender, about 3 minutes.
Add beans, corn, peas, green beans, and thyme. Stir to combine and cook for an additional 5 minutes.
Combine 1/2 cooked quinoa with the bean and mushroom mix. Transfer it to a large casserole dish.
Mix the remaining quinoa with melted butter and spread it on the top of a casserole mixture.
Place the casserole in the oven and bake for 10 minutes.
Garnish with chives and enjoy!