If using fresh octopus, freeze overnight. Thaw completely before cooking.
Place octopus in a large pot and cover with cold water. Add bay leaf, peppercorns, and 3 tbsp red wine vinegar. Do not add salt. Bring to a gentle boil, reduce to a low simmer.
Simmer for 45 minutes to 1 hour, until a knife slides easily into the thickest tentacle with little resistance and the octopus sags when lifted.
Remove from the pot and rest on a rack for 20-30 minutes. Pat dry.
Heat grill (or cast-iron grill pan) to the highest heat possible. Brush grates lightly with oil. Brush octopus with olive oil.
Grill 2-3 minutes per side until charred and crisped at the edges. Rest for 2 minutes, then cut tentacles at the joints.
Arrange on a plate. Dress immediately with olive oil, red wine vinegar, salt, pepper, dried oregano, and parsley. Serve with lemon wedges.