Slice the chicken breasts lengthwise into thirds, and then slice again into about 1-inch pieces. Place the chicken pieces in a freezer bag or bowl and set aside.

Add the Greek yogurt and olive oil to a medium size bowl. Zest one of the lemons into the bowl then juice that lemon with the remaining three lemons and add to the bowl. Add the minced garlic, oregano, kosher salt and black pepper and stir. Pour half of the marinade into the freezer bag or the bowl with the chicken pieces and reserve the other half of the marinade for basting. Marinate the chicken for 30 minutes or up to 3 hours in the refrigerator.

When ready to grill, prepare the grill by lightly oiling the grate with vegetable oil or cooking spray and set to medium high heat.

If using wooden skewers, prepare them by soaking in water for 10 minutes. If using metal skewers, no prep is necessary.

Thread the chicken on the skewers alternating with the red onion, zucchini and red bell pepper until you’ve reached the end of the skewer, ending with chicken. Repeat with the remaining skewers. Discard any of the remaining marinade that had the chicken in it.

Grill the chicken, basting the kebabs with the reserved marinade and turning often so each side browns and has light grill marks, until cooked through, about 10-15 minutes or until the chicken juices run clear. Serve warm with bbq sauce. Refrigerate leftovers for up to 3 days.