Scrub the quahogs clean and in a cast iron pan on your grill filled with an inch of water, steam the quahogs open. Discard any quahogs that do not open. Gently pry the shells open and remove the quahog meat, saving the shells. Toss with a drizzle of olive oil and grill for 30 seconds on each side. Remove from the grill, roughly chop, and set aside.

In the cast iron pan over the grill, sauté the sausage, onion, garlic, and breadcrumbs. Remove from heat and fold in the grilled, chopped quahogs.

Stuff the empty shells with about 1/2 cup of stuffing each and place on grill for 5 minutes, covered. To serve, whisk the olive oil, cilantro, lemon zest, and garlic. Drizzle over stuffed, grilled quahogs.