Preheat oven to 400F. Grease two 13x9 casseroles and set aside.
Cut each zucchini lengthwise and core using a small spoon to get the pulp out.
Place zucchini boats on the casseroles, spray with oil and sprinkle with salt and pepper.
Place in the oven until we are done making the ground beef filling.
Make the filling:
In a big skillet over medium high heat, pour olive oil and add diced onions.
Saute onions for about 3 minutes or until translucent.
Add garlic and continue to cook for 30 seconds.
Add ground beef break it apart and cook until no longer pink.
Drain excess fat if any then add mix in black pepper, oregano, tomato sauce and Worcestershire sauce.
Taste and adjust seasoning to your liking then let it continue to cook for another 2-3 minutes then turn heat off.
Take out the zucchini boats, they should be tender by now and almost fully cooked.
Divide the meat mixture into the boats and sprinkle evenly with shredded cheese.
Return to oven for another 5 minutes or until bubbly and cheese melts.