Saute in a medium skillet over low heat, stirring, until browned, about 10 minutes.
Lift from pan with a slotted spoon; discard any sausage drippings and wipe out the pan.
Heat the oil in the skillet; saute the peppers and onion over medium heat, stirring until edges begin to brown and vegetables are crisp-tender, about 5 minutes; add the garlic; saute 1 minute.
Return the sausage to the skillet; stir in the salt, oregano, and pepper; simmer, covered, 5 minutes.
Meanwhile, cook the pasta in plenty of boiling salted water until al dente, or firm to the bite, about 12 minutes; drain.
Toss with the sausage and pepper mixture and serve at once.