Fill a large bowl with cold water, add the wheat berries, and let soak for 10 to 18 hours. Drain. Bring 7 cups of water to a boil in a 4-quart pot over high heat. Add 3/4 tsp. salt. Add the wheat berries, reduce the heat to a simmer, and cook uncovered, stirring occasionally and adding more boiling water as necessary to keep the wheat berries covered, until tender, about 1 to 1-1/2 hours. Drain and rinse the wheat berries with cold water to stop the cooking.
Transfer the wheat berries to a foil-lined rimmed baking sheet, drizzle with 1 Tbs. of the olive oil, and toss lightly to coat. Spread the wheat berries on the baking sheet and cool completely at room temperature or in the refrigerator.
Put the vinegar in a small bowl and gradually whisk in the remaining 1/2 cup of olive oil. Whisk in the walnut oil. Taste and season with salt, pepper, and additional vinegar or olive oil as needed.
Put the cooked and cooled wheat berries in a large serving bowl and toss to break up any clumps. Add the green beans, corn, beets, blue cheese, chives, and 1/2 cup vinaigrette and toss. Taste and season as needed with more vinaigrette, salt, pepper, and serve.
The salad can be refrigerated for up to 1 day. If making ahead, let sit at room temperature so it’s not refrigerator-cold and season with more vinaigrette, salt, and pepper before serving.