Cook penne according to package directions, omitting salt and fat. Drain; transfer to a bowl. Whisk together olive oil, vinegar, sugar, salt, and pepper. Add dressing to pasta; toss.
Halve endive head; slice into 1/4-inch strips. Core half a head of radicchio; slice into 1/4-inch strips. Toss vegetables with pasta. Top with grated pecorino Romano cheese.
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