Heat olive oil in a large 12-inch skillet over medium-high heat.
Add the sliced sausage to the skillet and cook for 3 to 5 minutes, turning occasionally, until browned and crispy on the edges.
Use a slotted spoon to remove the sausage from the skillet and set aside on a plate.
Add the bell peppers, zucchini, and red onion to the remaining fat in the skillet. Sauté for 5 to 7 minutes until the vegetables are tender-crisp and lightly charred.
Add the minced garlic, oregano, salt, black pepper, and red pepper flakes to the pan. Cook for 60 seconds until fragrant.
Return the cooked sausage to the skillet and toss with the vegetables for 2 minutes to reheat and combine flavors.
Divide into bowls and serve immediately.