Preheat the oven to 350°F.
Slice the bread lengthwise and cross wise into a 3/4-inch grid, keeping the base crust of the bread intact. Lay the bread on a large sheet of heavy duty foil. Pry the bread grid open gently with your fingers and spritz lightly with spray olive oil or brush with olive oil. Stuff the cheese into the cuts in between and around the pieces of bread, reserving about 1/2 cup for the top of the bread. Sprinkle with the pepperoni dices, followed by the green onions and diced bell peppers. Wrap the foil up around the bread and crimp the top and ends. Bake for 20 minutes, or until the cheese is fully melted.
If desired, remove the foil wrapped bread from the oven and leave the ends crimped, but open it so the top of the bread is exposed. Return the packet to the oven and bake for another 8 to 10 minutes or until there are some golden brown areas of cheese. Serve while still hot by itself or with your favourite pizza sauce.