HEAT grill to medium heat.
GRILL chicken 5 to 7 min. on each side or until done (165ºF), brushing occasionally with 1/4 cup barbecue sauce for the last few minutes. Meanwhile, grill peppers and onions 4 to 5 min. or until crisp-tender, and grill tomatoes 2 to 3 min. or until tender, turning once.
MIX peanut butter and remaining barbecue sauce until blended.
CUT chicken and vegetables into strips; place on tortillas. Roll up tightly. Serve with peanut butter sauce.