Cut your chicken breasts into large chunks. (If you cut them too small the chicken can dry out.)
Toss the chicken in a large ziploc bag with all marinade ingredients. Squeeze out excess air and zip closed. Use your fingers to massage the marinade evenly around the chicken. Let sit for at least 30 minutes, flipping the bag over occasionally.
Slice zucchini, squash, and onion into large chunks. My squash and zucchini slices are about 1 inch thick.
Lightly coat your veggies with two tablespoons of olive oil. Generously season with salt and pepper.
Skewer your veggies and chicken.
Preheat grill to medium heat.
Place your kabobs on the grill. Grill for 5 -7 minutes, flip, and grill other side for another 5-7 minutes or until chicken is cooked through.
Optional: When I'm entertaining guests and want to add some extra wow I drizzle a little balsamic glaze over the top of these when plating. This is totally optional as they have plenty of flavor on their own. To make the glaze add 1/2 cup balsamic vinegar to a small pot. Heat to boiling. Reduce heat to low. You'll end up with small bubbles around the perimeter as it gently simmers. Let it continue simmering for about 10 minutes. Stir occasionally. It can burn quickly so keep an eye on it. Once it's reduced and thickened remove from heat. Drizzle over finished kabobs.
Notes
If your zucchini or squash are on the small side you'll want to use more so you have plenty of veggies on each kabob. Sometimes I use 3 of each.