Heat oven to 350°F. Cook ground beef in large skillet over medium-high heat for 2 to 3 minutes or just until browned, stirring frequently. Add bell pepper and onion stir-fry, and corn; cook 4 to 6 minutes or until beef is thoroughly cooked and vegetables are crisp-tender, stirring occasionally. Drain.
Add taco sauce, chili powder, garlic salt and cumin; mix well. Cook an additional 2 minutes.
Spread about 1/4 cup refried beans over each tortilla. Spoon ground beef mixture down center of each tortilla. Sprinkle each with cheese. Fold sides of each tortilla toward center; fold up ends. Place, seam side down, in ungreased 15x10x1-inch baking pan. Brush each filled tortilla with margarine.
Bake at 350°F. for 30 to 35 minutes or until golden brown and thoroughly heated. Serve with tomatoes and lettuce.