President Reagan doesn't think too highly of Wall Street's dour assessment of his economic program, and the decision last week to trim back proposed business tax breaks likely will add to the gap in expectations between his administration and the New York financial community.

For more comfort, maybe he should take his eye off the overemphasized Dow Jones average of 30 industrial stocks on the New York Stock Exchange and watch a stock market indicator that is computed every business day by a Washington investment company blocks from the White House.

Johnston, Lemon & Co.'s index of 30 Washington area corporation stocks hit another new high last week, closing Friday at 176.031 compared with 174.866 the previous week and about 117 a year ago.

After a brief interruption of a yearlong rally during late April, the Johnston, Lemon index resumed a steady ascent in early May. One of the major factors in the Johnston, Lemon game at a time when the Dow has been merely flirting with the magic 1,000 level for weeks is the composition of the local tax index: It includes New York and American Stock Exchange issues as well as over-the-counter stock. The Amex and OTC indices generally have been at or close to record levels in recent weeks.

Another major factor is the intense interest of local investors. Metropolitan Washington has more stock market investors per capita than any other area in the nation as well as a number of corporations that have attracted wide national investment attention.

MCI Communications Corp., for example, is consistently one of the most actively traded national stock issues every week. The D.C. firm, a pioneer in the new era of competition for long-distance telecommunications services with American Telephone & Telegraph, had a volume in the OTC market last week of 2.4 million shares. Only two issues in the New York Stock Exchange had higher volumes, International Business Machines at 3.4 million and Atlantic Richfield at 2.6 million.

With growing profits being recorded after initial start-up years that were characterized by a string of net losses, MCI's stock has increased in value by 80 percent since the start of 1981 to close last week at $23.88 a share. Details on MCI and other major regional companies are listed in the Washington Business table of 100 selected area stocks on page 13 in today's issue.

Of the 100 stocks that make up the weekly table, more than 10 percent hit new yearly highs in trading last week. Manor Care Inc., which expects a significant gain in business for its Quality Inns hotel subsidiary, jumped $5 a share last week, or 20 percent, to $29.75. That high point represents a 96 percent increase in stock price since the start of the year.

Other area stocks that hit yearly highs last week included Allegheny Beverage of Baltimore, where company officials said the acquisition of vending giant Macke Co. earlier this year has gone smoothy ($9.75, up 66 percent this year); First & Merchants Corp., a Richmond bank holding company that is joining other regional banks in benefiting from high interest rate returns on loans and interest in interstate banking ($26, up 24 percent); and Hechinger Co., with a continued sales boom for the do-it-yourself home repair business and successful entry into the Philadelphia market ($22.88, up 77 percent).

Also, International Bank of Washington, a diversified financial services firm ($11.63, up 18 percent); Overnight Transporation, a Richmond trucking firm with a strong record of earnings growth ($23.38, up 68 percent); U.S, Fidelity & Guaranty, a Baltimore insurance firm with similar growth records, ($46.38, up 9 percent); United Virginia Bankshares, the state's largest banking business and another beneficiary of regional banking attention ($36.38, up 35 percent); and the Washington Post Co., whose executives have forecast a stronger year than in 1980 ($28.50, up 26 percent).

Many other stocks are trading close to yearly highs, such as Geico Corp., holding company for a large automobile insurance firm and affiliates in other insurance or finance lines, which closed last week at $21.25, up 45 percent for the year. Geico's profitability from underwriting insurance has remained stable at a time when many firms in the property casualty business have been posting underwriting losses and relying on investment income to stay in the black.

One of the biggest gainers in recent weeks among area companies has been Bowl America, a northern Virginia-based operator of bowling centers in the D.C., Baltimore, Richmond and Florida (Orlando and Jacksonville) markets. Bowl America topped out at $7 a share before dipping slightly at the close last week to $6.88, a gain of 34 percent in the past month and 49 percent since the start of the year.

President Leslie H. Goldberg said there was no talk of mergers and acquisitions or other unusual developments behind the recent investor interest in this company. Rather, the consistent earnings performance of the company -- higher profits for 11 consecutive years -- recently has been called to the attention of some investors.

Raymond, James & Associates, a St. Petersburg, Fla., investment firm, probably spurred the new interest in Bowl America by concentrating on the Springfield firm in a May 18 weekly market letter.

Analyst Bert Boksen of Raymond, James noted that Bowl America has been expanding at a strong rate and that internal cash flow should finance adequately the expected addition of about one new bowling center every year (the company now has 26 centers with 936 bowling lanes). He projected annual earnings growth of 10 percent to 15 percent and a return of shareholders equity in a range of 17 percent to 19 percent.

About 50 percent of the 1.3 million Bowl America shares are now closely held, in part because the company itself has been buying back stock in recent years when the price was low. For the current fiscal year ending June 30, Raymond, James forecasts that Bowl America earnings will be up 15 percent to $1.05 a share from 91 cents in fiscal 1980.

Still another active gainer recently has been Avemco Corp., a Bethesda holding company for the nation's largers insurer of private aircraft, pilots and flying clubs. Avemco closed last week at $10.50 a share, off its yearly high of $13 but still up 25 percent since Jan. 1.

A new report from Bache Halsey Stuart Shields notes that Avemco has achieved a profit from underwriting insurance in 17 of the last 20 years, and its profit has averaged 15 percent over the last 18 years compared with an annual management goal of 15 percent underwriting profit as well as 4 percent premium sales growth.

Avemco's business prospects appear strong. For one thing, the Federal Aviation Administration has predicted that in the 1980s the number of active general aviation aircraft (Avemco's prime market) will jump 43 percent to 298,000, the number of hours flown will increase 45 percent to 61 million and the number of active pilots will pass one million -- up 25 percent 800,000 today.

In addition, Avemco is looking at such new markets as product liability insurance for manufacturer of aircraft components, homeowners and auto insurance for members of the Aircraft Owners and Pilots Association (avemco is official insurer for this 260,000-member group), liability insurance for commuter airlines, and packages policies for pilots and operators.

In addition to MCI, area utility stocks were among the most active local issues last week. Trading in Washington Gas Light Co. was unusually heavy at 183,000 shares. Early in the week, word came from Oklahoma that a major natural gas well there in which WGL has a 19 percent stake was being abandoned after mechanical problems in harnessing the huge flow had been discovered early in the year. That sent WGL stock down about $4 a share.

Washington Gas subsequently announced that a new well would be started adjacent to the previous site, indicating continued expectation of tapping the natural gas deep under Oklahoma farmland. By week's end, WGL stock had bounced back to a close at $29.75, off slightly from a week ago but up 37 percent from Jan. 1.