They're no longer fighting for their right to party. But when the spirit moves them, the boys can still be Beasties.

''Yeah, Prince is giving us a hard time for skateboarding on his walls,'' says a snickering Adam Yauch, a.k.a. MCA, one of three New York-bred rapper-musicians who comprise the Beastie Boys.

Seems the trio -- skateboard freaks all -- was rehearsing for its upcoming tour recently at Prince's Paisley Park studio complex outside Minneapolis. The room they were using, Yauch says, was conducive for some righteously rad rolling.

''The walls of the rehearsal studio are curved like a ramp,'' he explains, ''so we've been riding the walls. The people who work there keep coming out and yelling at us -- so bleeping soft!

''So we're gonna keep skating on there, anyway.''

Snotty, perhaps, but this particular antic is decidedly on the mellow end of the Beasties' raisin'-hell-o-meter. After all, the trio -- Yauch, Mike Diamond (Mike D) and Adam Horovitz (Ad-Rock) -- made its mark as uppity, obnoxious, rude 'n' lewd brats. Because of their seemingly terminal adolescent behavior, they've been banned from a couple of hotel chains and their record company's offices. Among their notable feats: negotiating a concert contract that called for a ''rainbow assortment'' of condoms; shaking up beer cans and spraying them on the audience; breaking into a sleeping writer's hotel room and pouring icy water on him.

Their mantra: ''Bein' bad news is what we're all about. We went to White Castle and got thrown out.''

Parents shuddered at such behavior, and large factions of the rap community balked at three rich white dudes doing their thing (this was before Vanilla Ice, mind you). But the Beasties laughed all the way to the bank.

On the back of their smash ''(You've Got to) Fight for Your Right (to Party),'' the Beasties' 1986 Rick Rubin-produced ''Licensed to Ill'' was rap's biggest selling album pre-Hammer. The three Beasties, who hail from well-heeled New York homes, became teen demigods, but their tongues were clucking in their cheeks all the time.

The Beasties of the '90s, however, are decidedly different creatures. They've matured and moved to Los Angeles. Horovitz, 25, is acting (his latest film is ''Roadside Prophets''). Diamond, 26, who was accepted at Harvard, helps run the group's affairs and has some business interests on the side. Yauch, 27, once the surliest Beastie of all, is now a macrobiotic vegetarian who has become interested in Eastern philosophies.

Their music also has undergone change, starting with 1989's ''Paul's Boutique'' and continuing with this year's ''Check Your Head.'' Though still rapping, the trio broadened its stylistic reach on ''Head'' and, most dramatically, picked up the instruments they abandoned before they made the sample-heavy ''Licensed to Ill.''

''We kinda got back into it from the stuff we were sampling on our other records,'' explains Yauch, who plays bass. ''A lot of the records we were listening to (in order) to find loops and samples had really amazing playing on it. We had a lot of funk records that had these really great instrumentals. You listen to that playing, and . . . it got us into playing again.''

The move brings the Beastie Boys full circle to the days of the Young and the Restless, a hard-core punk band Yauch and Diamond formed in 1980. After hooking up with Horovitz, the son of playwright Israel Horovitz, the trio recorded ''Cookie Puss,'' a rap-style parody of a New York ice cream commercial that was a smash in dance clubs and hooked them an opening spot on Madonna's 1985 tour.

''We couldn't play 'Cookie Puss' live,'' Diamond explained in 1987. ''The only thing we could do like it was rapping.'' So the instruments were traded in for a disc jockey and a turntable, and the Beasties didn't pick up their instruments again to record until after ''Paul's Boutique.''

They did so enthusiastically. ''Most of the stuff we played on ('Check Your Head') was done first,'' Yauch says. ''We got back into the more rhythmic, rapping stuff later on.''

With its combination of cocky raps (''Finger Lickin' Good'') and tight, Stax-Volt style groovers (''In 3's'') -- plus a salute to Motor City Madman Ted Nugent in ''The Biz vs. the Nuge'' -- ''Check Your Head'' is a decided departure from the debauchery that was the Beasties' trademark.

But they don't seem to be suffering for it. The album landed in Billboard's Top 10 its first week out, and the early shows on the tour have all been sell-outs.

Which means Yauch and his mates can keep rolling -- on skateboards or up record charts.

''Everyone's got their two cents,'' says Yauch, whose father was raised in Dearborn and who still has family in the area. ''There were definitely people saying, 'You guys should play, man,' and others who were saying 'Nah, don't do it. Just keep rhyming.' Back when we were a hard-core band and we started rhyming, we had people telling us not to do that, too.

''You're always going to get some of that. Change is inevitable, and so is growth, but I guess there are people who just want you to stay the same way forever.

''But we refuse.''