Place all the vegetables in a large bowl and add the oil. Season to taste and stir gently to coat.
Heat a large griddle pan over a high heat, add half the vegetables and cook for about 2 minutes each side until lightly charred. Remove from the pan and keep warm while you cook the remaining vegetables in the same way.
Divide the vegetables between 4 serving plates, drizzle with the lemon juice, then spoon the pesto over them. Serve immediately with focaccia.