Start by cleaning the octopus. Remove the beak and innards, and rinse thoroughly.
Bring water to a boil in a large pot. Add the octopus and simmer for 30-40 minutes until it becomes tender. Drain and let it cool.
In a mixing bowl, combine olive oil, minced garlic, lemon juice, dried oregano, salt, and pepper. This will be your marinade.
Place the boiled octopus in a Ziplock bag and pour the marinade over it. Refrigerate for at least 2 hours while sealing the bag.
Preheat your grill to medium-high heat.
Remove the octopus from the marinade and grill for about 3-4 minutes per side until it gets a nice char and grill marks.
Serve your Greek grilled octopus with lemon wedges and fresh parsley for garnish.