Remove tempeh from packaging, and cut each block in half, to make square “steaks”. Place in a steamer basket, and steam the tempeh for 15 minutes.
Meanwhile, heat the olive oil in a heavy, oven-proof skillet, and sauté onions until caramelized, about 20-30 minutes.
Remove onions from skillet. Add a little more oil if needed.
Add the tempeh to the skillet, and sauté about 5 minutes on each side, until browned.
Remove tempeh from skillet. Pour in cooking wine and broth, and return the onions, along with the grapes and chopped rosemary to the skillet. Simmer about 5 minutes. The grapes will begin to swell and burst.
Nestle the tempeh back into the skillet, turning once to coat both sides. Bake in the oven 15-20 minutes, until grapes begin to shrivel and the liquid is mostly gone from the pan.