Mix beans, tomatoes, chili powder and oregano in saucepan. Cover and simmer 5 minutes. Uncover and simmer, stirring and crushing some of the beans against side of pot, 5 minutes longer. Set aside. Warm tortillas per package directions and keep warm under a hot, damp cloth. Place 1 tablespoon of bean mixture on center of each tortilla. Sprinkle with a rounded teaspoon of onion, then a tablespoon of cheese. Fold opposite sides of tortillas on top of mixture twice, forming square packets. Place fold sides down on nonstick pan. Repeat until all ingredients are used. Cook over low heat, covered, 3 to 5 minutes until heated through and bottoms are crispy.

Serve at once or keep warm on a covered warming tray.

Yield: Makes 6 to 8 servings (22 to 24 pieces).