Season the shrimp with salt & pepper. Heat 2 tablespoons of the olive oil in a large sauté pan and quickly sauté the shrimp for about 2-3 minutes until pink in color. Remove from the pan and portion into smaller ovenable plates/bowls.
Heat the remaining olive oil in the sauté pan and cook the onions over medium heat until softened; about 8 minutes. Add the garlic, red pepper flakes, oregano and cook for 2 additional minutes. Add the ground tomatoes and simmer for 2-3 minutes.
Taste the sauce, adjust the seasonings and pour evenly over the portioned shrimp servings.
Just prior to service, top each of the portions with the crumbled Feta cheese. Broil or bake the shrimp until the Feta melts.
Garnish with the fresh parsley and serve with the grilled sliced bread.