Preheat oven to 350 degrees F (180 degrees C). Heat oil in a skillet set over medium-high heat. Cook onion, celery and pepper until softened, about 5 minutes. Stir in ketchup. Remove pan from heat and divide sauce mixture in half.

Combine one half of the sauce with ground beef, breadcrumbs, egg, salt and pepper. Mix gently. Pat mixture into a lightly greased 9-x 5-in (2 L) loaf pan. Bake for 1 hour or until an instant read thermometer reaches 160 degrees F (70 degrees C).

Rest for 5 minutes. Reheat the reserved sauce mixture. Slice meat loaf and serve with sauce.