In a large bowl, cream together the softened butter, mayonnaise, garlic powder, and black pepper. Add the green olives, black olives, shredded pepper jack cheese (reserving 1/2 cup), and parsley. Mix to combine.
1/2 cup Unsalted butter, 1/2 cup Mayonnaise, 1/2 tsp Garlic powder, 1/4 tsp Black pepper, 6 oz Pimento-stuffed green olives, 6 oz Black olives, 1/2 cup Fresh parsley, 8 oz Pepper Jack cheese