SLICE onions, keeping the sliced white bottoms and green tops separate. Heat oil in large skillet on medium-high heat. Add meat; cook 5 min. or until evenly browned, stirring occasionally and adding garlic for the last minute. Stir in teriyaki sauce, bell peppers, crushed pepper and white onion slices. Pour into slow cooker; cover with lid.
COOK on LOW 5 to 6 hours (or on HIGH 3 to 4 hours).
MIX cornstarch and dressing until blended. Add to slow cooker with snow peas and nuts; stir. Cook, uncovered, 10 min. or until slightly thickened. Top with green onion slices.