First, cook the spaghetti squash.

Preheat the oven to 400 F. Poke holes in the outside of the squash and place on a baking sheet. Bake 45 minutes to 1 hour.

Spray a large skillet with nonstick spray coating and heat over medium high heat.

Add turkey. Cook, stirring occasionally, for 5 minutes.

Drain fat and discard.

Stir in tomatoes with their juice, green pepper, onion, garlic, oregano, and black pepper.

Bring to a boil; reduce heat.

Simmer covered for 15 minutes, stirring occasionally.

Remove cover; simmer for 15 minutes more. (If you like a creamier sauce, give sauce a whirl in your blender or food processor.) 

Once squash is cool, slice lengthwise and scoop out seeds with a spoon.

Serve sauce over scooped spaghetti squash or in the squash "boats."