Dice the onion and cook in a medium sauté pan over medium high heat until they are soft. While the onions are cooking, drain the beans and rinse them with cold water.
Mash beans, chili powder, and ketchup until they form a chunky paste.
Fold in the cooked onions, oats, and the beaten egg.
Let the mixture rest for a few minutes then divide it into 4 equal amounts. Using wet hands shape mixture into four equal patties.
Preheat the oil in a medium sauté pan over medium high heat.
Cook the patties, about 5 minutes each side until browned.
Top each patty with lettuce, tomato, onion and enjoy!