MLG WAS SLOW TO TURN TO ASSIGNED HEADING AND THEN TURNED TO WRONG HEADING.

Narrative

WE HAD BEEN HOLDING AT THE ODDLY INTXN DUE TO A RWY CLOSURE AT STL. WE WERE LOW ON FUEL BUT STILL LEGAL. THERE WAS SOME TENSION DUE TO THE LOW FUEL SITUATION. AT APPROX XA05 WHILE BEING VECTORED BY APCH THE CTLR GAVE US A LEFT TURN TO A HDG OF 210 DEG. THE CAPT READ BACK THE CLRNC OF LEFT TO 210 DEG. AT THIS TIME COMPANY WAS CALLING ON THE OTHER RADIO; IT WAS A DISTR SO I WAS TURNING THE VOLUME DOWN ON THE COMPANY RADIO. BEFORE I COULD GET MY HAND TO THE HDG CONTROL OF THE AUTOPLT THE CAPT TURNED IT AND THE ACFT STARTED A LEFT TURN. AT THIS TIME THE CAPT SAID 'LET'S TURN THIS THING AROUND'. SINCE IT WAS MY LEG; THAT IS I WAS FLYING AND THE CAPT WAS THE NON FLYING PLT; HIS TURNING THE ACFT SURPRISED ME FOR A SECOND. I LOOKED UP AND SAW AN LGT AT 12 O'CLOCK AND APPROX 7 MI. I POINTED IT OUT TO THE CAPT AND REMARKED THAT THAT WAS THE ACFT WE WOULD BE FOLLOWING ON THE APCH. IT WAS AT THIS TIME I NOTICED THAT WE HAD TURNED THROUGH OUR ASSIGNED HDG OF 210 DEG. I DISCONNECTED THE HDG MODE OF THE AUTOPLT AND QUICKLY TURNED BACK TO 210 DEG. ALL THIS HAPPENED IN JUST A FEW SECONDS. THE CAPT HAD TURNED THE HDG CONTROL TO 120 DEG. I SHOULD ADD THAT THE COMPANY I FLY FOR LIKES US TO FLY EVERY OTHER LEG AND USES A SYSTEM OF FLYING PLT AND NON FLYING PLT. THIS IS TO SAY THAT THE FLYING PLT MAKES ALL THE TURNS; CLIMBS AND DESCENTS AND SO ON (HE FLIES THE ACFT). THE NON FLYING PLT PERFORMS THE DUTIES OF THE NON FLYING PLT AND MONITORS THE FLYING PLT. HE DOES NOT MAKE TURNS. THE CAPT STILL HAS THE FINAL SAY. IT IS ALL IN OUR OPERATIONS MANUAL. IF WE EACH DO OUR JOB AND NOT PART OF THE OTHER'S JOB WITHOUT SAYING WHAT WE HAVE DONE; THINGS LIKE THIS WOULD NOT HAPPEN. I LIKE TO DO THINGS IN A DELIBERATE MANNER AND NOT RUSH; I FEEL IT IS SAFER THAN RUSHING AND I SEEM TO GET THERE JUST AS FAST AS THE REST OF THE PEOPLE I FLY WITH. THE COCKPIT IS NO PLACE FOR CONFUSION AS TO WHO DOES WHAT AND WHO DID WHAT. (IMAGINE THAT YOU ARE DRIVING YOUR CAR AND THE PERSON NEXT TO YOU GRABS THE WHEEL AND TURNS THE CAR AND YOU GET PENALIZED FOR HIS ACTIONS; HOW WOULD YOU FEEL?) I HOPE THAT THIS WILL HELP OTHERS FROM MAKING THE SAME MISTAKES AS WE MADE. I WILL BE WATCHING THE NON FLYING PLT CLOSER.