Heat olive oil in a large skillet over medium heat. Add minced garlic and red pepper flakes, sautéing for about 1 minute until fragrant.
Add the sliced calamari to the skillet and cook for 2-3 minutes, stirring frequently, until they turn opaque.
Stir in the diced tomatoes, black olives, capers, and oregano. Season with salt and pepper. Bring the mixture to a simmer and cook for an additional 5-7 minutes, allowing the flavors to meld.
Serve the calamari puttanesca over cooked pasta and garnish with fresh parsley.