BROWN meat with onions in large skillet on medium heat; drain. Return to skillet.
ADD gravy, ketchup and mixed vegetables; stir. Simmer 5 min. or until heated through, stirring occasionally. Meanwhile, cut VELVEETA into 4 slices, then cut each slice in half.
SPOON potatoes over meat mixture. Arrange VELVEETA pieces in spoke-fashion over potatoes; cover. Cook on low heat 3 min. or until VELVEETA is melted.