Heat oven to 350° F.
In a medium Dutch oven, combine the oil, lemon juice, onion, thyme, garlic, ¼ cup water, 1½ teaspoons salt, and ¼ teaspoon pepper.
Trim the top and bottom of each artichoke. Using scissors, snip the tip off each leaf. Cut the artichokes into quarters and scoop out the fuzzy chokes.
Toss the artichokes in the oil mixture. Cover, transfer to oven, and cook until tender, about 45 minutes. Divide among individual plates and spoon the cooking liquid over the top.