Boil octopus in salted water until cooked through (check inside with a paring knife), 15 to 20 minutes. To a metal bowl add oil, oregano, pepper flakes, garlic, lemon juice, parsley, salt and pepper, then add octopus and toss.
Preheat a grill to high heat.
Place octopus on the grill for 3 to 4 minutes, then transfer back to bowl and back to grill. Repeat this step a few times. Finally, put octopus back in bowl and add balsamic vinegar. Toss well, then serve over baby greens.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.