Spread mashed potatoes evenly in a 2-quart casserole dish; set aside. Brown the venison in a large skillet over medium-high heat until crumbly and no longer pink, set aside.
Heat the canola oil in the skillet, then stir in the red onion, garlic, celery, and red bell pepper. Cook until the onion has softened, about 3 minutes. Stir in cooked venison, and season with Worcestershire, salt, and pepper. Spoon mixture onto potatoes in the casserole dish.
Stir together eggs and cottage cheese in a small bowl; spread evenly over meat mixture. Top with tomato slices, and sprinkle with cheese.
Bake, uncovered, in preheated oven until set, about 20 minutes.