Heat oil in a large, heavy skillet over medium heat. Crumble the tofu coarsely and add to hot skillet in a single layer. Cook, without stirring, until the tofu begins to brown, about 5 minutes. Stir gently to turn and continue cooking until uniformly golden brown. Add tomatoes, mushrooms, garlic, basil and oregano and cook about 5 minutes more. While sauce is cooking, brush polenta slices lightly with olive oil; place on broiler pan and broil a few minutes until toasted and golden. Stir feta cheese into sauce and serve over polenta slices.