Spray a large skillet with cooking spray. Turn heat to medium-high. Drizzle a small amount of oil into pan (this method allows you to attain flavor of oil without too much added fat). Chop potatoes and onion. Carefully drop potatoes and onions into pan; season with salt and pepper. Cook until browned and softened. Stir occasionally so as to avoid sticking to pan. Once done, set aside and cover.
While potatoes are cooking, whisk together eggs. Heat an additional smaller sized skillet over medium heat; spray with cooking spray. Dice pepper and saute for 2-3 minutes. Add eggs and scramble; cook until no longer runny. Just as eggs finish cooking, add chopped spinach. Remove from heat so spinach will just barely wilt.