Heat olive oil in a large skillet over medium heat.
Add the sliced onions to the skillet and sauté until translucent, about 5–7 minutes.
Stir in the minced garlic and cook for another minute until fragrant.
Add the chicken sausage slices to the skillet, cooking until heated through and browned, around 5–7 minutes.
Incorporate the chopped sun-dried tomatoes and oregano, seasoning with salt and pepper.
Cook for an additional 3–5 minutes to combine the flavors, stirring occasionally.
Remove from heat and garnish with fresh basil before serving.