Preheat oven to 400°F. Brown beef in large skillet on medium-high heat. Drain fat. Add beans, tomato sauce, chili powder, 1 teaspoon of the oregano and garlic powder; mix well. Bring to boil. Reduce heat to low; simmer 5 minutes.
Prepare corn muffin mix as directed on package, adding remaining 1 teaspoon oregano. Spoon batter into 12 greased and floured or paper-lined muffin cups, filling each cup 2/3 full. Spoon beef mixture into each cup, gently pressing into batter. Sprinkle with cheese.
Bake 12 minutes or until edges of muffin cups are golden. Cool 5 minutes in pan on wire rack. Top each cup with sour cream and green onions.