In San Francisco, people telephone for groceries with a timed delivery

''Would you stop at the market on your way home and pick up . . . .'' This phone call and the items it requests can often be pretty lengthy - and, for sure, time-consuming. Now, San Francisco has a new local service to help out those who have trouble squeezing the grocery shopping into that everyday list of things to do.

Called Grocery Express (''The All-delivery Market''), it boasts 46 courier-employees who serve some 4,000 regular customers by direct-phone-and-truck-delivery six days a week in the Bay Area.

''Basically, we're a warehouse operation,'' said John Coghlan, an executive of the 18-month-old organization. ''Clients can telephone orders from our 3,200 food-item catalog and get same-day delivery at an appointed time. We stock only well-known brand names but go beyond that by offering 'full services' - like fresh produce, cut-up poultry, meat-to-order, frozen foods, almost everything for the family dinner table and the home.''

Grocery Express sets a minimum order at $20 and charges customers $2.75 for each delivery, right to the door. Most customers - once they try the service - stay on as regulars. About 60 percent are young married couples, both working, who phone the service once a week. The balance are working singles or older individuals, some with restricted mobility; these phone shoppers tend to order every other week.

Mr. Coghlan says Grocery Express catalog items are priced competitively at retail - about 6 percent above national independent grocery chains. Customers pay on delivery - cash, credit cards, food stamps, personal checks, or through the company's own pre-deposit account. Bay Area phone shoppers to Grocery Express follow a general pattern of ordering, buying about 11 percent dairy and 11 percent fresh produce items, and 17 percent meat and poultry, with the balance in household staples including frozen foods. Average orders run about $ 58.

''It was our idea from the beginning,'' Mr. Coghlan went on, ''to offer a unique service - something that if once tried could become sort of addictive. That's about what happened. Our prices proved to be right; but more than that, customers like the conveniences we were selling. For example, many of our older customers use us because they don't want to have to make the trek outside to the store. And more - they don't want to have to wheel or tote the stuff home. Young marrieds, on the other hand, say they use us because they can call from the home or office (7:30 a.m. to 7:30 p.m.) and arrange to meet our delivery trucks later at home.''

Unlike many of today's retailers, which do not quote delivery truck arrival times, Grocery Express routes its deliveries within two-hour segments from 8 a.m. through 10 p.m., and it is proud of its on-time performance.

To attract new customers, the company makes direct mailings to selected area householders in and around San Francisco. The latest effort hit 160,000 addresses with a free $3 credit on the first trial order. Unlike myriad-item listings on conventional supermarket advertising, Grocery Express copy includes only a few limited specials on food. It relies heavily on the free-credit hook to entice first-time buyers and to sell ''the market that comes to you.''