Place a large pot over medium-high heat and coat with the grapeseed oil. Add the collard greens, chicken stock, onions, 1/4 teaspoon kosher salt, 1/2 teaspoon pepper and 1/4 teaspoon seasoning salt. Mix in the smoked turkey. Turn the heat to low and cook, covered, until the greens are tender but not too soft, 35 minutes.