COMPETITION: Amazon’s Whole Foods Deal Adds Pressure on Grocery Services to Deliver.

Now, with the e-commerce giant planning to buy Whole Foods WFM -0.31% Market Inc. for $13.7 billion, giving it a large foothold in the food retail industry, the stakes are all the higher for companies such as Instacart Inc., Peapod LLC, Shipt Inc. and FreshDirect LLC to deliver not only fresh food—but continued growth.

Midwestern grocery chain Schnucks Markets Inc. is expected Thursday to announce its partnership with Instacart for online delivery will extend to most of its 100 stores by next month. Ahold Delhaize’s Peapod is expanding its push into New York City, a key market, after spending more than $94 million on a warehouse in Jersey City, N.J., in 2014.

Shipt, which delivers food orders for retailers including Costco Wholesale Corp. COST 0.57% , Meijer Inc. and Whole Foods, intends to almost double its markets by next year, from 51 to 100. Founder Bill Smith says the company’s expansion is targeting suburban customers in less saturated regions like the South and the Midwest to gain an edge.

The largest U.S. food sellers, Wal-Mart Stores Inc. WMT 0.66% and Kroger Co. KR 2.55% , meanwhile, are testing delivery services using Uber Technologies Inc. and Lyft Inc.

My wife and I have been mostly happy ordering online for delivery (King Sooper) or for pickup (Walmart). We have only two complaints. One is that the quality of the produce is hit or miss, and if you need some meal-critical veggies or the ripest fruit, you’re still better off getting it yourself. The other is that their online ordering frontends are simply not very good, which seems like an area where competition from the online-shopping giant ought to force improvements.

But delivering only the best produce — reliably, affordably, and at a profit — is the Holy Grail of online grocery shopping. The first company to figure that one out stands to dominate.