Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Drizzle the bread slices with olive oil. Grill the bread until golden on both sides, about 2 to 3 minutes per side. Remove the bread, and squeeze the lemon juice over the bread slices. Sprinkle the bread slices with dried oregano, salt, and pepper.
In a medium bowl combine the ricotta, tomatoes, 3 tablespoons mint, salt, and pepper. Gently stir to combine.
To serve, either spoon the cheese topping over the bread and sprinkle more chopped mint over the bruschetta for garnish, or place the cheese topping in a bowl and serve with the grilled bread alongside.