Preheat the oven to 450°. In a small bowl, blend the butter with the juniper and season with salt and pepper.
In a large skillet, heat 1/4 inch of vegetable oil until shimmering. Season the squabs with salt and pepper. Add 4 of the squabs to the skillet, breast side down, and cook over moderately high heat, turning a few times, until richly browned all over, about 12 minutes. Repeat with the remaining squab, adding more oil to the skillet as needed.
Arrange the squabs breast side up on a large, rimmed baking sheet. Rub the squab cavities with the juniper butter. Arrange two bacon halves on each squab breast in a single layer. Scatter the grapes around the squab and roast in the upper third of the oven for about 15 minutes, until an instant-read thermometer inserted in the thickest part of the legs registers 125° for medium-rare meat. Transfer the squab to a carving board and let rest for about 5 minutes.
Using a large knife, cut each squab in half, cutting through the breast bone. Transfer the squabs to plates. Spoon the grapes and roasting juices on top and serve.
Suggested Wine Pairing
Earthy, gamey squab is an ideal partner for an Italian Merlot blend.