Prepare all of the ingredients.
In a saucepan over medium heat, add marinara ingredients. Stir to combine and cook 5 minutes. Reduce heat to medium-low and let simmer until ready to serve.
In a bowl, combine green peppers, red onions, pepperoni, garlic powder and Italian seasoning.
In a saute pan over medium-high heat, add Italian sausage. Cook and crumble until no longer pink. Add to pepperoni mix.
Preheat griddle to high. Build quesadillas: Add ¼ cup cheese, spoonful of pepperoni mix, then ¼ cup cheese to half of tortilla. Fold over and place on griddle. Cook for 5 minutes on each side. Repeat with remaining tortillas.
Cut each quesadilla into thirds. Serve with ramekin of sauce and 1 or 2 quesadillas per serving.