In a dish large enough to fit a masher, place garlic cloves and cover with 1 Tbsp of olive oil. Microwave on high for 3 minutes. Set aside to cool.
In a small dish, mix oregano, bell pepper, parsley, garlic granules, black pepper, salt, and remaining lemon zest. Combine half of the spice mixture, remaining lemon zest, butter, and garlic cloves. Mash well.
Prepare the chicken, removing excess fat and patting dry. Using your fingers, gently separate the skin from the breast and thigh.
Spread the mash evenly under the skin atop the breast and thighs.
Place cut lemon and onion quarters inside chicken. Truss chicken.
Put chicken, breast side up, in dutch oven.
With the remaining half of the spice mixture, combine with 2 Tbsp of olive oil and brush over entire chicken.