Preheat oven to 350 degrees F. Spray a loaf pan with nonstick spray.
In a medium skillet, heat 1 tablespoon of the olive oil. Add the peppers, onion and garlic and cook until just soft. Remove from heat and cool.
When the peppers and onion are cooled, mix the remaining ingredients together minus the marinara. Use your hands to pack the meat mixture into the loaf pan, or if you are not using a loaf pan, shape the meat into a loaf and set on a baking sheet or oven dish. Top evenly with marinara.
Bake for 50 to 60 minutes or until an instant-read thermometer, inserted in the middle of the meatloaf, reads 160 degrees F. Remove from the oven and let rest 5 minutes before slicing and serving.
Source: Adapted from Michael Chiarello, The Food Network