In a large saucepan over low heat, heat 1/4 cup oil. Add onions, scallions and salt, stirring occasionally, for 5 to 10 minutes. Add garlic and cook about 2 minutes more. Add rice and another 1/4 cup olive oil and stir to combine. Add raisins, pine nuts, mint, dill and parsley. Add 1 cup boiling water and simmer, covered, for about 5 minutes. Remove from heat and add juice of 1 lemon.
Separate grapevine leaves and rinse under water to remove brine. Drain. Remove thick stems with a sharp knife. Place 1 tablespoon filling on underside of leaf, which should be facing up on your work surface. Starting at the base, roll over, fold in sides and continue to roll tightly toward the leaf point.
Line a medium saucepan with a few heavy grapevine leaves. Place bed of parsley stalks over leaves. Arrange stuffed grape leaves, seam side down, in layers. Sprinkle with remaining 1/4 cup olive oil and remaining lemon juice. Weigh grape leaves down with heavy plate. Add boiling water so that it covers stuffed leaves. Bring water back to the boil, reduce heat to a simmer and cover saucepan. Simmer slowly for about an hour, until rice is tender. Simmer longer if necessary. Allow to cool to room temperature, remove from water mixture and chill. Serve cold with additional lemon wedges for sprinkling on at service.