I don't know if this is the recipe you've lost. I do know this recipe is great.
From Mollie Katzen's Still Life with Menu.

Roasted and Marinated Green Beans with Onions and Garlic Cloves

3 to 4 T olive oil
1 lb fresh green beans, trimmed
1 medium red onion, sliced thin
6 to 8 cloves garlic, peeled & sliced in half
1/2 t salt
1 to 2 T balsamic vinegar
pepper to taste

Preheat oven to 400. Brush large baking tray with 2 T oil. Spread beans, onions & garlic on tray. Drizzle with remaining oil, and salt.
Bake 20 to 30 minutes, tossing several times. When beans are tender, remove to bowl and toss immediately with vinegar and pepper. Serve hot, room temp or cold. Serves 4.

I've added walnuts to the roast with success. This is also good cold, tossed with feta cheese.