Preheat oven to 325°F. Heat oil in large sauté pan over medium heat. Add onion; cook, stirring occasionally until tender, about 3 minutes.
Add pot roast and cook, stirring frequently for 3 minutes. Divide meat mixture among 6 heatproof individual serving dishes.
Layer each dish with 1/3 cup vegetables and ¼ cup gravy. Top with ½ cup mashed potatoes, spreading to edges to seal. Repeat with remaining ingredients.
Spray potatoes with non-stick cooking spray. Bake for 20 minutes or until center of casseroles are 145°F.
Recipe and photo courtesy of Tyson