RWY EXCURSION. PLT FATIGUE IMPROPER THROTTLE MOVEMENT.

Narrative

FO FLEW APCH AND LNDG AT ORD ON RWY 27R. LNDG AND ROLLOUT DECELERATION NORMAL. I ASSUMED CTL BELOW 60 KTS AND CONTINUED SLOWING FOR THE HIGH SPD L TURNOFF. SEVERAL SECONDS AFTER STOWING THE SPD BRAKE; THE L ENG ACCELERATED TOWARD FULL PWR AND THE ACFT ACCELERATED INTO A R TURN AND WENT INTO THE GRASS. FO SAW THE L THROTTLE FULL FORWARD AND PULLED IT BACK; THEN PUT BOTH ENGS INTO FULL REVERSE. ACFT STOPPED ON GRASS AND PARALLEL TO RWY 27R. PAX REMAINED SEATED UNTIL DEPLANED BY MOBILE STAIRS. NO INJURIES OR DAMAGE EXCEPT TO CAPT'S EGO. WHILE THE FLT RECORDER DATA IS UNAVAILABLE; I AM CONFIDENT THAT I PUT THE L THROTTLE FULL FORWARD BY MISTAKE WHILE THINKING THAT I WAS STOWING THE SPD BRAKE. AFTER FLYING THE B737- 300 FOR 3 1/2 YRS; THE HABIT OF STOWING THE SPD BRAKE BY ADVANCING THE L THROTTLE WAS WELL INGRAINED. THE 757/767 FLEET ON ACR X RETRACT SPOILERS BY MANUALLY PUSHING THE LEVER FULL FORWARD TO THE DETENT. I SUSPECT THAT FATIGUE (LAST LEG OF A 4 DAY TRIP WITH CONSECUTIVE VERY EARLY STARTS) CAUSED ME TO REVERT TO HABIT PATTERNS AND I HAD A NEGATIVE TRANSFER FROM THE B737. MY 3 MONTHS ON THE B757 WAS NOT ENOUGH TO OVERCOME THE B737 HABIT. SUGGESTED FIX: STANDARDIZE SPOILER RETRACTION PROCS AMONG ALL FLEETS SO THAT THERE IS NO NEGATIVE HABIT PATTERN CARRYOVER WHEN A PLT MOVES TO ANOTHER TYPE ACFT. SUPPLEMENTAL INFO FROM ACN 324182: WHILE CAPT WAS TAXIING ON HIGH SPD I LOOKED DOWN TO CHANGE UHF RADIO FREQ. I FELT THE ACFT TURN 90 DEGS TO THE R; LOOKED FORWARD AND NOTED L THROTTLE WAS ADVANCED. I RETARDED THROTTLE; PLACED BOTH ENGS IN REVERSE AND APPLIED FULL WHEEL BRAKES. ACFT DEPARTED PAVED TXWY AND CAME TO REST HDG 270 DEGS IN GRASSY AREA S OF AND ADJACENT TO RWY 27R.