1Arrange onion and celery in bottom of slow cooker (this will act as an oven rack to help cook chicken more evenly). Rub chicken with olive oil, garlic powder and oregano; place on top of onion and celery.

2Cover and cook on High setting for 3 to 4 hours or Low setting for 6 to 8 hours or until chicken is cooked through and meat thermometer inserted into thickest part of inner thigh registers 185° F (85° C).

3Remove chicken, celery and onion from slow cooker. Let cool until easy enough to handle. Using 2 forks, shred chicken and return to slow cooker. Chop celery and return to slow cooker; discard onion.

4Using electric mixer, beat together cream cheese and sour cream until smooth; stir in Buffalo sauce. Add to slow cooker; toss with chicken mixture, 2 cups (500 mL) Cheddar and 1/4 cup (60 mL) blue cheese until combined. Sprinkle remaining Cheddar and blue cheese over top.

5Cover and cook on High setting for 60 to 75 minutes or Low setting for 2 to 3 hours until hot and bubbly. Sprinkle shredded lettuce and green onions over top. Serve with a medley of tortilla chips, pita chips and crackers.