Heat olive oil in a 12-inch cast-iron skillet over medium-high heat until shimmering.
Add the sliced sausage in a single layer and sear for 3-4 minutes per side until deeply browned and the fats have rendered.
Transfer the sausage to a side plate, leaving the rendered fat and oil in the skillet.
Incorporate the bell pepper, zucchini, and onion into the skillet. Sauté for 8-10 minutes, stirring occasionally, until the vegetables are tender-crisp and slightly charred.
Reduce heat to medium; add the minced garlic, oregano, and smoked paprika. Stir constantly for 60 seconds to prevent the garlic from burning.
Return the cooked sausage to the skillet and toss thoroughly with the vegetable mixture to combine flavors and reheat.
Adjust seasoning with sea salt and black pepper according to taste preference.
Distribute the mixture evenly into four bowls over the pre-cooked quinoa or brown rice base.