Chicken and Summer Vegetable Enchiladas Verde

INGREDIENTS

• 2 Tbs. vegetable oil, plus more for brushing
• 1/2 large red onion, diced
• 1 zucchini, diced
• 1 cup fresh corn kernels
• 2 oz. baby spinach, cut into 1/8-inch strips
• 1 cup cooked and shredded chicken breast
• Kosher salt and freshly ground pepper, to taste
• 5 oz. Monterey jack cheese, shredded
• 1 jar (1 lb. 9 oz.) green enchilada starter
• 12 corn tortillas, each about 6 3/4 inches in diameter
• Sour cream for serving
• Avocado slices for serving