Brush beef with 1 tbsp oil and preheat a frying pan until hot. Season beef with salt and pepper and cook on each side for 2-3 minutes until medium rare, cover loosely and rest for 5 minutes, then slice thinly.
Cook quinoa according to packet directions until tender, drain. Allow to cool slightly.
Combine remaining oil and white balsamic. Season.
Combine quinoa, radicchio, grapes, basil and feta in a large bowl, drizzle with dressing and divide amongst serving bowls, serve with sliced beef.