ZFW CTLR EXPERIENCED OPERROR AT 5000 FT WHEN ASSIGNING IFR STATUS TO AN IN TRAIL ACFT BEFORE VERIFYING ALT STATUS OF THE SECOND ACFT.

Narrative

I WAS WORKING MAF-LO; ABI-LO R AND D COMBINED. THERE WERE SCATTERED CELLS OF PRECIP ON THE EASTERN SIDE OF MAF-LO AND GENERALLY CLR IN ABI-LO. ACFT X CALLED ON FREQ HAVING DEPARTED ZZZ REQUESTING IFR CLRNC TO AUS. ACFT X HAD A PROPOSED IFR FLT PLAN IN URET FROM ZZZ DIRECT AUS REQUESTING 9000 FT. I DEPARTED THE FLT PLAN AND ASSIGNED ACFT X A DISCRETE CODE. ACFT Y THEN CALLED ON FREQ STATING HE HAD JUST DEPARTED ZZZ; WAS IMMEDIATELY BEHIND ACFT X; REQUESTED TO FOLLOW HIM DIRECT AUS; AND WAS CLBING TO 5000 FT. ACFT Y HAD A PROPOSED FLT PLAN IN URET FROM ZZZ DIRECT LLO DIRECT AUS REQUESTING 7000 FT. I DEPARTED THE FLT PLAN AND ASSIGNED ACFT Y A DISCRETE CODE. I STARTED TRACKS ON EACH FLT. NEITHER ACFT WERE IN RADAR CONTACT. THE NORMAL ALT FOR RADAR CONTACT IN THAT AREA IS ABOUT 5000 FT. I ISSUED ACFT X A CLRNC DIRECT AUS CLBING TO 9000 FT. ACFT X READ BACK THE CLRNC CORRECTLY AND RPTED LEAVING 4600 FT. I THEN INSTRUCTED ACFT X TO RPT LEAVING 5000 FT. MY INTENTION WAS TO USE ALT LEAVING IN ORDER TO ASSIGN ACFT Y AN IFR CLRNC DIRECT AUS AT 5000 FT. ACFT X RESPONDED THAT HE WAS LEAVING 5000 FT AT THIS TIME. I THEN ISSUED ACFT Y DIRECT AUS AND CLB AND MAINTAIN 5000 FT. ACFT Y ACKNOWLEDGED THE CLRNC AND STATED THEY WERE OUT OF 5200 FT AND GOING BACK DOWN TO 5000 FT. ABOUT THAT TIME THE DATA BLOCKS BEGAN TO ACQUIRE AND CONFLICT ALERT ACTIVATED. IN A FEW SECONDS; I OBSERVED ACFT X LEAVING 6000 FT AND ACFT Y AT 5000 FT. ZFW MGMNT AND QUALITY ASSURANCE CONCLUDED THAT THE OPERROR OCCURRED BECAUSE I FAILED TO OBTAIN A RPTED ALT FROM ACFT Y PRIOR TO ISSUING HIM AN IFR CLRNC WHILE THE ACFT WAS BELOW RADAR COVERAGE AND THAT NO SEVERITY ERROR HAD OCCURRED PER 7210.682.