WRQX-FM (107.3) is hoping for a winner this time around. The Top 40 station debuted its third morning team in less than a year yesterday morning, after firing J.J. McKay at the end of his breakfast shift Friday. Relative newcomers to the business, Chris Jagger and "Mad Mike" Bryant, who have soared to the top of the teen ratings pile with their four-hour evening program, have been bumped up to the coveted morning drive.

The move pits them against WAVA-FM's (105.1) aggressive and antagonistic "Morning Zoo" team of Don Geronimo and Mike O'Meara. The "Zoo" team has been climbing the ratings ladder steadily and is ranked second in the market, behind WMAL-AM's (630) perennial favorites, Frank Harden and Jackson Weaver.

"It's like a dream come true," said Jagger, who is 28 and now, because of almost endless staff changes during the past year, the ABC-owned station's senior announcer. He joined Q-107 as an overnight disc jockey two years ago and describes his climb to the top as "a Cinderella story."

Jagger's evening material was "youth oriented," with such hokey yet popular segments as "Love Lines," in which he'd act as a go-between, requesting dates for teen-age listeners too shy to ask for themselves. That part of Jagger's repertoire, however, will not move to mornings.

Bryant, 24, who grew up in Silver Spring, started his career as an intern at sister-station WMAL-AM and began screening phone calls during Jagger's program last fall. He was slowly worked into comedy bits and joined the show in March.

"Jagger has demonstrated to me that he is really a talented person," Q-107 program director Chuck Morgan said Friday. "I think his kind of show can be transferred to mornings and attract a lot of adults 18 to 49. We plan on making some revisions to appeal to a wider spectrum of listeners."

Morgan expects some of that need to be filled by Celeste Clark when she returns in two weeks to the morning show from middays.

McKay, 32, who also grew up in Silver Spring (his real name is Larry Sullivan), was hired in early December with partner "Christian Paul" Gironda after Morgan conducted an extensive nationwide search for a team to replace Jim Elliott and Scott Woodside. That team split up last July 25. Gironda left Q-107 suddenly at the beginning of June for Boston, where he joins that city's "Morning Zoo" at WZOU-FM on Monday. McKay and Gironda, like the team before them, were said to be arguing constantly when the mikes were off.

Max Is Back

Max Reznick was back in the saddle Sunday morning, hosting "The Max Reznick Show" after nearly five weeks off because of illness. Reznick is said to be responding well to treatment for a brain tumor and was able to host his two-hour program of news and information and traditional Jewish songs, which begins at 9 a.m. on WNTR-AM (1050). The show, known for awarding a barbecued chicken, three pints of ice cream or a dozen bagels to the listener with the correct "Yiddish Word of the Week," is in its 41st year on radio here and is thought to be the longest running ethnic radio show in the country.

The Ears Have It

About 4 million people a week are tuning in Bruce Williams' weeknight financial advice show, and NBC Talknet likes that. Enough so that Williams last week was signed to another five-year contract that will have him in the dough and talking about the stuff through 1992. Weekend Talknet gabber Bernard Meltzer has gotten the opposite message from NBC. He has been replaced by Bob Madigan, a correspondent for NBC's young adult network, the Source, since its inception in 1979. Madigan will discuss financial matters on weekends. Talknet is heard on WWRC-AM (980).

Around the Dial

Each day this week, WGMS-AM/FM (570/103.5) will air highlights of the University of Maryland International Piano Festival and William Kapell Competition at College Park. The performances can be heard at 6:05 p.m. through Friday. On Saturday at 8:30 p.m., the National Symphony will back up finalists in a live concert broadcast from the Kennedy Center . . . WHUR-FM (96.3) is presenting a five-part news series on AIDS each morning this week at 8:55. The five-minute segments feature live interviews with health experts and wind up Friday at 6:40 p.m. with a special edition of "Insight" hosted by Herman Washington . . . Former NBC-TV late night authority Tom Snyder has finally jumped to radio. He's signed on with the ABC Talk network, again burning the midnight oil, from 10 p.m. to 1 a.m. However, no local affiliate is carrying the show at this time ... "Downtown Vinnie Brown," formerly of WOL-AM (1450), Q-107 and most recently the overnight shift at WMZQ-FM (98.7), has left for the program director's slot at new WQOK-FM in South Boston, Va. The 100,000-watt urban contemporary station is aimed at the fast-growing Raleigh-Durham, N.C., market.