Final answer:
The corporate strategy being employed is vertical integration.
Step-by-step explanation:
The corporate strategy being employed when a large grocery store purchases a dairy farm to supply all of the store-brand milk, yogurt, butter, and cheese is vertical integration. Vertical integration is when a company acquires or controls the supply chain of its products, either backward into production or forward into distribution. In this case, the grocery store is vertically integrating by owning a dairy farm to ensure a consistent and reliable supply of dairy products for its store-brand items.