In saucepan, cook onion in oil. Stir in chili powder, cumin, garlic, and salt. Cook 1 min. Cool. Stir in beans, rice, cheese, milk, and eggs. Spray a 10" microwave-safe pie plate with nonstick spray. Add rice mixture. Cook, uncovered, 50% power, 22-24 mins or until center is just set, giving dish a quarter turn, twice. Let stand 10 mins. Garnish with chopped green pepper and serve with salso if desired.