2) In a mixing bowl, whisk together the orange marmalade, garlic, oregano, mustard and vinegar. Stream the olive oil into the dressing while whisking; season with salt and pepper.
3) Pull off 8 of the outer leaves of the radicchio. Form serving cups for the pasta salad from the leaves using 2 leaves to form each bowl. Chop the remaining radicchio.
4) Toss the chopped radicchio, pasta and chopped onions with the dressing to combine. Serve the pasta in the lettuce bowls.