Heat olive oil in a large skillet over medium heat.
Add the sausage pieces to the skillet and cook until browned, about 5-7 minutes.
Remove the sausage from the skillet and set aside; keep the drippings in the pan.
Add the sliced onion and bell peppers to the skillet, cooking until soft, about 5 minutes.
Stir in the minced garlic and cook for another minute, until fragrant.
Return the browned sausage to the skillet, along with the canned tomatoes and oregano.
Season with salt and pepper, then bring to a simmer.
Cover and let simmer on low heat for 10-15 minutes until heated through.