1. Preheat the oven to 220 °C. Bring 400 ml of water with some salt to the boil in a pan.
  2. Add oat grains and cook slowly for 10 minutes.
  3. Mix in buckwheat and quinoa and cook the grains al dente in 15 minutes.
  4. In a roasting pan, mix bell pepper strips with grapes and radicchio.
  5. Sprinkle with salt and freshly ground pepper and drizzle 2 tablespoons olive oil over it.
  6. Roast in the oven for 15-20 minutes until al dente. Stir every now and then.
  7. Mix spinach through roasted vegetables and slide roasting pan into the oven for another 3-5 minutes, until spinach shrinks.
  8. Let vegetables cool until lukewarm.
  9. Make a dressing of orange juice, orange zest, mustard and 3-4 tablespoons olive oil in a bowl and mix in warm grain mixture. Leave to cool until lukewarm.
  10. Spoon grains on plates and divide roasted vegetables over them.
  11. Serve salad lukewarm.