Preheat the oven to 375°F. In a mixing bowl, combine the ground beef, rolled oats, egg, 2 tablespoons of the teriyaki sauce, and diced onion. Mix until evenly combined.
Shape the mixture into a loaf and place it in a loaf pan. Spread the remaining 2 tablespoons of teriyaki sauce over the top.
Bake the meatloaf for 45 minutes, or until it reaches an internal temperature of 160°F. Remove from the oven and let it rest for 5 minutes.
While the meatloaf rests, heat the vegetable oil in a large skillet over medium-high heat. Add the frozen mixed vegetables and cook for 2 minutes.
Stir in the cooked white rice and pineapple chunks. Cook for 3 minutes, breaking up any rice clumps.
Push the rice mixture to one side of the skillet. Crack the eggs into the empty space and scramble them until set, then mix everything together.
Add the soy sauce and sliced green onions. Stir well and cook for 1 more minute. Slice the meatloaf and serve with the pineapple fried rice.