TONIGHT'S AGENDA Noon Call to order. Platform debate continues. 7 p.m. Invocation, presentation of colors, national anthem, and pledge of allegiance. 7:10 p.m. Willie Nelson to sing the national anthem. 7:12 p.m. Israel Moushowitz to lead in the Pledge of Allegiance. 8:20 p.m. Rep. Mary Rose Oakar of Ohio introduces Gov. Edmund G. Brown Jr. of California. 8:22 p.m. Gov. Brown speaks. 9 p.m. Start of process for selection of presidential nominee, followed by announcement of nominee and the benediction. RADIO-TV COVERAGE

Today's radio and television coverage of the Democratic National Convention:

NBC-TV's coverage begins at 7:30 p.m.; CBS' at 8.

ABC-TV will broadcast from the convention from 7:30 to 8 p.m. and from 9 p.m. until the proceedings end.

The National Public Radio Network (WETA -- 90.9 FM) will broadcast gavel to gavel, beginning at noon. CONVENTION UPDATE

Monday: Kennedy loses roll-call vote on "open" convention, 1,936.4 to 1,390.6. Ninety minutes later, he withdraws as a candidate.

Tuesday: Delegates approve Kennedy's $12 billion antirecession jobs program, but reject his proposal for immediate wage and price controls and a plan for immediate comprehensive national health insurance. In an emotional appearance before the convention, Kennedy predicts that the party will reunite for the fall campaign, but stops short of an explicit personal endorsement of Carter.