Steak, roasted pepper & pearl barley salad

INGREDIENTS

• 85g pearl barley , rinsed
• 1 red pepper , deseeded and cut into strips
• 1 yellow pepper , deseeded and cut into strips
• 1 red onion , cut into 8 wedges, leaving root intact
• 1 tbsp olive oil , plus a little extra
• 1 large lean steak , around 300g, trimmed of any excess fat
• ½ x 100g bag watercress , roughly chopped
• juice ½ lemon , plus wedges to serve (optional)