Last season, the Highlanders pushed St Johnstone all the way for third place and a Europa League place, but there was a clear gulf in class between the two sides here, with Nigel Hasselbaink and David Wotherspoon putting the Perth side two goals to the good after 18 minutes.
Wotherspoon would miss from the spot shortly before half-time, but it mattered little as Stevie May and Dave Mackay netted after the interval to seal a comprehensive win.
County boss Derek Adams made half a dozen changes after a disappointing home defeat by promoted Partick Thistle, but the Staggies look a pale shadow of the team which finished last season so strongly.
The Highlanders were unable to test 41-year-old Saints debutant Stevie Banks, who started in the Perth goal in place of the injured Alan Mannus, ruled out for six weeks with a shoulder injury.
After the hosts slowly turned the screw, Hasselbaink tucked away the opener in the 14th minute with a cheeky back heel finish from midfielder Murray Davidson's low cross.
It got worse for County four minutes later when Wotherspoon curled home a superb 30-yard free-kick, finding the top corner to open his account after a summer switch from Hibernian.
Defender Scott Boyd was booked for the foul on rumoured Peterborough United target Stevie May which teed-up the free-kick.
Then Wotherspoon was tripped in the box in the 38th minute by full-back Ben Gordon.
But the dominant midfielder's effort from the penalty spot was parried at full-stretch by goalkeeper Mark Brown and May struck the rebound effort over the bar.
But County remained on the rack before half-time and Davidson's run onto a superb Hasselbaink pass ended with a shot which rolled past the post with County in disarray.
Stevie MacLean skilfully set-up strike partner May in the 49th minute and the Scotland Under-21 international cut inside Gordon and lashed a low shot through keeper Brown to put Saints three goals to the good.
In the 62nd minute, skipper Mackay stroked a 25-yard free-kick round the defensive wall to leave Brown flat-footed for goal number four.
It should have been five minutes later but Frazer Wright skied a volley wide after being picked out at the back post by star man Wotherspoon.
It mattered little to the overall result, however, as Saints cruised.