HEAT oven to 350°F.
ADD beans to large saucepan of boiling water; cook on medium heat 4 to 6 min. or until crisp-tender. Rinse with cold water; drain.
COOK bacon in same saucepan on medium heat until crisp. Remove bacon from skillet with slotted spoon; drain on paper towels. Discard all but 2 Tbsp. drippings from skillet. Add onions to reserved drippings; cook and stir 4 min. or until tender. Stir in flour. Gradually stir in milk until well blended; cook and stir 3 min. or until thickened. Add cheese; cook and stir 3 min. or until melted.
STIR in beans and bacon; spoon into 1-1/2-qt. casserole sprayed with cooking spray. Top with cracker crumbs.
BAKE 25 min. or until heated through.