In a large bowl mash the beans with a fork. Crumble the beef into the bowl and sprinkle with chili powder, pepper, and salt. Mix well. Shape into 6 2 1/2-inch patties.
Heat oil in a large skillet over medium-high heat. Add patties. Cook for 2 minutes per side or until done.
Serve patties in pita bread rounds topped with cheese, salsa, and lettuce.