Preheat char-grill or barbecue grill plate on high heat until hot. Spray both sides of the mushrooms with olive oil and season with salt and pepper. Cook, stalk side down for 2 minutes, turn mushrooms over and cook a further 2 minutes or until mushrooms are just tender. Transfer to a platter.
Top mushrooms with a dollop of pesto, crumble over the feta. Serve topped with micro herbs or wild rocket leaves.