COMBINE VELVEETA and RO*TEL in 1-1/2-qt. microwaveable bowl. Microwave on HIGH 5 to 6 min. or until VELVEETA is completely melted and mixture is well blended, stirring every 3 min. Stir in chicken and onions.
HEAT large nonstick skillet on medium-high heat. Spoon about 1/2 cup chicken mixture onto half of 1 tortilla; fold in half. Add to skillet; cook 1 min. on each side or until golden brown on both sides. Remove from skillet. Repeat with remaining tortillas and filling.
CUT into wedges.
Special Extra: Garnish with chopped fresh tomatoes just before serving.