what temperature to bake a potato in oven
1 Don't preheat the oven. 2  Prick your sweet potatoes each 2-3 time with a fork, then place them directly on the oven rack in the middle of the oven, above the foil. 3  Turn the oven on to 425. 4  Bake for 45 minutes for sweet potatoes/yams that are 2-3 inches in diameter. Turn the oven on to 425. 2  Bake for 45 minutes for sweet potatoes/yams that are 2-3 inches in diameter. 3  For sweet potatoes that are up to 4 inches in diameter, bake for an hour. 4  For super large sweet potatoes, bake for an hour and 15 minutes.