Cook sausage over medium heat, breaking up into pieces with fork, about 5 minutes. Transfer to bowl with slotted spoon.
Add onions and garlic to skillet. Cook until golden-brown, stirring frequently, about 4 minutes. Add peppers and oregano. Cook until peppers are tender, stirring occasionally, about 3 minutes. Add to sausage and gently stir in potato. (can be prepared 1 day ahead – cover and refrigerate).
Preheat oven to 350 degrees F.
Cut bread in half horizontally with long, serrated knife. Remove doughy center, leaving a 1 inch shell. Flatten shells lightly with rolling pin. Brush shells with 2 tblsps olive oil. Reassemble loaf and wrap with foil. Place in oven to warm.
Beat eggs to blend in large bowl. Mix with sausage mixture and season to taste.
Remove bread from oven.
Heat remaining 1 tblsp oil in 8 inch non-stick skillet over medium heat. Add egg mixture and swirl with rubber spatula. Cook until bottom is light brown and eggs are slightly soft on top, about 5 minutes. Transfer omelette to broiler and cook until top is just set, about 2 minutes longer.
Unwrap bread and slide omelette onto bottom half. Cover with top, cut into 6 wedges and serve. (this is good hot or cold).