A million-dollar commodity business from a lake-bluffs bunker

James Spencer stopped his stroll along the wooded path to scratch the bright pink wattle of a large turkey, one with a splendid spread of feathers. ''This is Tom, and that is his bride, Mabel,'' Mr. Spencer told his visitor, pointing to the much smaller, brownish turkey pecking at the path. ''They are our good friends. But we would never be allowed to take them into 'the Pit' down in Chicago.'' He was referring to the Chicago Board of Trade, of which he is a former member.

Laughing, Spencer led the reporter to the door of the snug concrete block building that serves as office and family home. The structure with its two satellite receiver dishes on the roof is hidden among woods about 200 yards in from the narrow blacktop road that ribbons along the bluffs above Lake Michigan.

No roadside sign or mailbox indicates the business that's conducted there in the woods. Yet for more than two years the J. M. Spencer & Co. brokerage firm has bought and sold commodity futures. Clients are not the Midwest industrialists whose families have been summering here for more than a century. The Spencers handle the portfolios of more than 100 clients, 90 percent of them on the East Coast or in Europe. They're associated with Fidelity Investments of Boston.

''We can get into the Pit faster by telephone than a guy down there can get across the floor to it,'' Mr. Spencer says. ''It's nothing for us to move a million bucks in the market in 30 seconds.''

About four years ago, Jim and Sharon Spencer and their children, Samantha and Jimmie, decided that living in a lofty apartment in a glass tower on Chicago's Outer Drive was not the way they wanted to raise their two children. They settled on farming as a way of life and a hedge against inflation (which they contend will accelerate). Mr. Spencer sold his memberships in the Chicago Board of Trade and Winnipeg Grain Exchange.

After a two-year search the Spencers found 79 acres of cedar, swamp, springs, and higher ground with syrup-producing maple trees, a clearing for hard fruit trees, and the site on which to build their four-bedroom home next summer.

Already they have dug a pond largely without help. Water flowing out of it will generate electricity. It has been stocked with brook trout and provides good swimming. It also adds to the view from the home that is to be built on a cleared field just above it.

The family has gathered a flock of chickens, geese, and the turkeys, Tom and Mabel. The children collect the chicken eggs and sell them, in boxes they designed, to regular customers. They do many other chores. In season they pick edible wild mushrooms and blueberries, which they also sell.

''It's a zoo around here on Saturdays,'' Jim said happily. ''We go collect the kids' friends in our mini bus fairly early and then their parents come to get them in late afternoon and stay around for tea and conversation.''

Their first accomplishment was the construction of the ''Brokerage Cabin,'' the concrete block building in which the family sleeps and eats, which is the center of the trading the Spencers conduct.

Fed in by the satellite dishes, commodity prices flash along a Trans-Lux Jet board that dominates the wall that faces an entering visitor, while financial news unfolds on a Reuters teleprinter.

In a triangular room back of the board are crowded a Steinway grand piano, bookshelves, a sofa, and a small table. The children's bunks, clothing, and toys are neatly arranged in another corner room, the kitchen and bath in other nooks and crannies.

''Our hobby is research,'' Mr. Spencer explains. ''Macroeconomic research, dealing with worldwide cyclical values, inflation effects, interest rates, and economic growth patterns. We put that to work in the markets, mainly the futures markets, for our clients on a straight commission basis.

''I sometimes miss the excitement of the Pit,'' he says, ''but then I remember they would never allow me to keep Tom and Mabel there.''