Preheat oven to 350 degrees F. Season turkey legs with black pepper, Heat grapeseed oil in a large deep pot over medium-high heat. Add turkey legs and brown in batches on all sides. Transfer to a roasting pan, cover with foil, place in oven and roast until fork tender, about 35 minutes.
Add garlic to pot and lightly saute over medium heat being careful not to burn the garlic. Stir in the crushed red pepper and shredded cabbage and allow to cook about 10 minutes. Add collard greens and cook for 10 minutes more. Add spinach, season with salt and freshly ground black pepper and cook until tender but still bright green. Transfer greens to a platter and top with turkey legs.