Raw, fennel is cool and crunchy. Cooked, fennel turns mellow and the flesh softens; it is perfect as a side dish for fish or chicken.
Preheat oven to 425 degrees. Trim fennel bulbs. Halve bulbs lengthwise; slice lengthwise into 1/2-inch-thick pieces.
On a rimmed baking sheet, toss fennel with oil; season with salt and pepper. Roast, turning once, until browned, 25 to 30 minutes.