Preheat oven to 300°. Place tortilla shells in a warmer or a covered casserole dish. Heat until warm.
Heat oil in a large skillet and sauté onion for 1 to 2 minutes. Add rice and beans and refried pinto beans. Mix thoroughly. Cover and simmer on low until hot, stirring frequently to prevent burning.
When the shells and rice and beans are hot, place a lettuce leaf on each shell. Place an equal amount of rice and beans on each. Add red pepper strips, sliced avocado, and salsa. Roll up, serve, and enjoy.
Per serving - 521 calories, 18 g fat (30% calories from fat), 15 g protein, 79 g carbohydrate, 12 g fiber, 0 mg cholesterol, 958 mg sodium